A process for producing hydrogen

Abstract

The present invention relates to a process of producing hydrogen gas from water vapor in the presence of an alkali metal, which is being recycled through the process.

Description

A PROCESS FOR PRODUCING HYDROGENTECHNICAL FIELD

[0001] The present invention relates to a process of producing hydrogen gas from the reaction of water with alkali metal, which is being recycled and reused.BACKGROUND

[0002] Hydrogen (H2) serves as a fundamental raw material in the chemical industry. It is also considered as the most likely alternative for fossil fuels in transportation, particularly due to its high energy-to-weight ratio and clean combustion products (water). Over 65 million metric tons of commercial hydrogen are produced today, with the bulk of the production utilizing fossil fuel, or biomass, in addition to water as resources. Approximately 95% of production relies upon steam methane (CH4) reforming (SMR) or other methods utilizing fossil fuels. SMR involves mixing superheated steam (H2O) (700°C to l,100°C) with de-sulfurized natural gas in a reforming reaction to produce hydrogen and carbon monoxide (CO). The carbon monoxide then interacts with 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 is very energy intensive and has a large carbon footprint, as the production of a single kilogram (kg) of hydrogen gas generates about 7 kg of carbon dioxide (CO2) emission.

[0003] Hydrogen is typically classified by colors, depending on its production processes: GREEN, where typically hydrogen is produced by electrolysis of water, using electricity from renewable sources, such as wind and solar energies; BLUE, where typically hydrogen is produced from fossil fuels where the CO2 produced is captured and either stored or ; GREY, where typically hydrogen is extracted from natural gas using steam-methane reforming, as detailed above; PURPLE / PINK, where typically hydrogen is produced by electrolysis using nuclear power; TURQUOISE, where typically hydrogen is produced by thermal splitting of methane, thereby solid carbon is produced instead of CO2; BROWN / BLACK where typically hydrogen is produced by coal gasification; YELLOW, where typically hydrogen is produced byelectrolysis using grid electricity from various sources (renewable and fossil fuels); and WHITE, where typically hydrogen is produced as a byproduct of industrial processes.

[0004] GB patent No. 1436350 describes a process for the recuperation and conversion of thermal energy, wherein at least part thereof is supplied to a given alkali metal monoxide (X2O), where X represents either sodium (Na) or potassium, to decompose said monoxide to form the given alkali metal dioxide (X2O2) and the given alkali metal (X); said dioxide is reacted with water to form the given alkali metal hydroxide (XOH) and gaseous oxygen (O2), which is separated, recovered, and partially recycled; and said metal is reacted with said hydroxide to form the given alkali metal monoxide (X2O), which is recycled, and gaseous hydrogen (H2), which is separated and recovered.

[0005] WO 2015 / 093547 discloses a method comprising a first hydrogen generation step in which an alkali metal and an alkali metal hydroxide are reacted to generate an alkali metal oxide and a hydrogen molecule; a reduction step of decomposing the alkali metal oxide produced in the first hydrogen generation step to produce an alkali metal and oxygen molecules; a second hydrogen generation step of reacting the alkali metal produced in the reduction step with water to produce an alkali metal hydroxide and hydrogen molecules, wherein the first hydrogen generation step, the reduction step, and the second hydrogen generation step are performed in this order.

[0006] Miyaoka et al. (International Journal of Hydrogen Energy 37 (2012) 17709- 17714) investigates thermochemical water-splitting by sodium redox reactions. The reaction system consists of three separate reactions, which are hydrogen generation by NaOH-Na reaction, metal separation by thermolysis of Na2O, and oxygen generation by hydrolysis of Na2C>2.

[0007] There is still an unmet need for a cost-effective production of hydrogen gas that has minimal energy input and employs water as a hydrogen source.SUMMARY

[0008] The following embodiments and aspects thereof are described and illustrated in conjunction with compositions and methods which are meant to be exemplary and illustrative, not limiting in scope. In various embodiments, one or more of the above-described problems have been reduced or eliminated, while other embodiments are directed to other advantages or improvements.

[0009] The present invention provides processes for splitting of water through a cycle of reactions, which involve alkali metal reduction of the water and regeneration of the alkali metal in order to be recycled in an additional cycle of reactions.

[0010] In is to be understood that throughout the present disclosure, the terms ’’metal” and “alkali metal" refer the zero oxidation-state of the metallic element, unless specified as a metal oxide or a constituent in metal oxides (i.e., a metal cation).

[0011] As used herein, the term “water-splitting” relates to any process that generates elemental hydrogen or oxygen from water as the starting material.

[0012] The process of the present invention involves three main reactions, which are described in steps (b), (d) and (f) herein. Collectively, the three reactions and the additional required steps result in the desired product through water-splitting and regeneration of the alkali metal, which enables further recycling.

[0013] Specifically, the reaction of step (b), according to some embodiments, involves reduction of water using the alkali metal (MA), as follows:

[0015] Specifically, the reaction can be made, according to some embodiments, with excess alkali metal over reacted water as detailed below and as reflected by:

[0017] wherein a is greater or equal to b.

[0018] Importantly, it was found that for the purpose of conducting the present sequence of reactions in one reactor system, the water needs to be provided as gas mixture comprising water vapor and an inert gas, which is generally non-typical for such reaction sequences and commercial production. According to some embodiments, the gas mixture comprises about 1.2% to 3.2% water vapor v / v in the inert gas.

[0019] According to some embodiments, the reaction in step (d), according to some embodiments, is performed under separate conditions of those of step (b) and involves the reduction of the alkali metal hydroxide (MA0H) using the alkali metal (MA), as follows:

[0020] MA+ MA0H MA2O + 1 / 2H2.

[0021] Importantly, it was found that for effectively carrying out this reaction as part of the present reaction sequence, a temperature (or temperature gradient) Td, which is in the range of 100°C to 600°C 200°C to 450°C, or 300°C to 450°C, is required.

[0022] Lastly, according to some embodiments, the reaction in step (f), according to some embodiments, is performed under separate conditions of those of steps (b) and (d) and involves a thermal decomposition under vacuum of the alkali metal oxide (MA2O) to recycle the alkali metal, as follows:

[0024] Importantly, it was found that for effectively carrying out this reaction as part of the present reaction sequence, a temperature Tf, which is in the range of 400°C to 1000°C and a sub-atmospheric pressure Pf(e.g., in the range of 0.1 torr to 100 torr), are required.

[0025] Additionally, the present process involves the recycling of the alkali metal formed in step (f) as a starting material for an additional cycle, i.e., for use in step (b) as described herein.

[0026] Further provided is a reactor system, which is configured to carry out the present process, according to some embodiments.

[0027] Thus, according to some embodiments, there is provided a process for water splitting, the process comprising:(a) providing a gas mixture comprising water vapor and an inert gas;(b) contacting the gas mixture with an alkali metal, to form hydrogen and a mixture of the alkali metal (MA) and alkali metal hydroxide (MA0H);(c) optionally, isolating the hydrogen produced in step (b) from the mixture of the alkali metal and alkali metal hydroxide;(d) adjusting the temperature of the mixture of step (b) to a temperature Td, which is in the range of 100°C to 600°C to induce a reaction between the alkali metal and alkali metal hydroxide, thereby forming hydrogen and an alkali metal oxide (MA2O);(e) isolating the hydrogen produced in step (d), and optionally, the hydrogen produced in step (b) from the alkali metal oxide;(f) adjusting the alkali metal oxide formed in step (e) to a temperature Tf, which is in the range of 400°C to 1000°C and a pressure Pfin the range of 0.1 torr to 100 torr, to induce a decomposition of the alkali metal oxide into a recycled alkali metal and oxygen;(g) isolating the recycled alkali metal produced in step (f), wherein the process further comprises repeating steps (a) to (g) at least once, by reusing the recycled alkali metal isolated in step (f) for subsequent use in repeated step (b).

[0028] According to some embodiments, the gas mixture of step (a) comprises water vapor at a relative humidity of 10% to 100% in the inert gas. According to some embodiments, the relative humidity is in the range of 20% to 100%, 30% to 100%, 40% to 100%, 50% to 100%, 60% to 100% or 70% to 100%. Each possibility represents a separate embodiment of the invention. According to some embodiments, the relative humidity is in the range of 50% to 100%.

[0029] According to some embodiments, the gas mixture of step (a) comprises 0.5% to 3.2% water vapor v / v in the inert gas, including each value and sub-range within the specified range. According to some embodiments, the gas mixture of step (a) comprises 1.2% to 3.2% water vapor v / v in the inert gas.

[0030] According to some embodiments, step (a) comprises providing an aqueous composition and flowing an inert gas over or through the aqueous composition, thereby forming the gas mixture, so it includes the inert gas with a predetermined humidity. According to some embodiments, step (a) comprises providing an aqueous salt solution and flowing an inert gas over or through the aqueous salt solution, thereby forming the gas mixture. According to some embodiments, the aqueous salt solution is a saturated aqueous salt solution. According to some embodiments, the salt is selected from the group consisting of ammonium nitrate, ammonium sulfate, magnesium chloride, magnesium nitrate, lithium chloride, potassium sulfate, potassium nitrate, potassium chloride, potassium acetate, potassium hydroxide, sodium chloride, sodium nitrite, sodium dichromate and combinations thereof. According to some embodiments, the salt is potassium sulfate.

[0031] According to some embodiments, the gas mixture provided in step (a) comprises steam and the inert gas. According to some embodiments, the steam is superheated steam.

[0032] According to some embodiments, step (a) comprises (i) providing an aqueous composition and flowing an inert gas over or through the aqueous composition, thereby forming the gas mixture, so it includes the inert gas with a predetermined humidity; and / or (ii) providing gas mixture comprising water steam and an inert gas.

[0033] According to some embodiments, the gas mixture provided in step (a) is substantially devoid of water aerosol.

[0034] According to some embodiments, the gas mixture is provided in step (a) at a temperature Tain the range of 5 °C to 600°C. According to some embodiments, temperature Tais in the range of 15°C to 40°C.

[0035] According to some embodiments, the alkali metal of step (b) is sodium.

[0036] According to some embodiments, step (b) comprises contacting the water within the gas mixture with the alkali metal, wherein the alkali metal is in a molar excess over the contacted water. According to some embodiments, the molar ratio between the alkali metal and the contacted water is in the range of 1.5:1 to 2.5:1.

[0037] According to some embodiments, step (b) comprises flowing the gas mixture into a first reaction chamber of a reactor, the first reaction chamber contains the alkali metal, at a flow rate and time period that results in a molar ratio between the alkali metal and the water reacting therewith to be in the range of 1.5: 1 to 2: 1, to induce the following reaction:wherein a is greater or equal to b, thereby forming the hydrogen and the mixture of the excess alkali metal and alkali metal hydroxide.

[0038] According to some embodiments, step (b) further comprises monitoring the transformation of the alkali metal into the alkali metal hydroxide, and to stop flowing the gas mixture into the first reaction chamber when the molar ratio is reached.

[0039] According to some embodiments, the first reaction chamber comprises a first gas inlet and a first gas outlet, wherein step (b) comprises:flowing the gas mixture through the first gas inlet into the first reaction chamber to contact the alkali metal, induce the reaction and form the hydrogen and the mixture of the excess alkali metal and alkali metal hydroxide; and flowing the formed hydrogen, the inert gas and optionally water vapor through the first gas outlet, thereby maintaining a pressure Pbwithin the first reaction chamber.

[0040] According to some embodiments, step (b) is performed at a pressure Pbof about 1 Bar.

[0041] According to some embodiments, step (b) is performed at a temperature Tbin the range of 5 °C to 600°C.

[0042] According to some embodiments, temperature Tbis in the range of 15 °C to 40°C.

[0043] According to some embodiments, the process further comprises isolating the hydrogen produced in step (b) from the mixture of the alkali metal and alkali metal hydroxide in step (c).

[0044] According to some embodiments, step (b) comprises: providing a reactor contains the alkali metal and comprises a first reaction chamber, the first reaction chamber comprising a first gas inlet and a first gas outlet, and flowing the gas mixture through the first gas inlet into the first reaction chamber, thereby contacting the water with the alkali metal and forming the hydrogen and the mixture of the excess alkali metal and alkali metal hydroxide; and step (c) comprises flowing the formed hydrogen, the inert gas and optionally water vapor through the first gas outlet, thereby isolating the hydrogen produced in step (b) from the mixture of the alkali metal and alkali metal hydroxide.

[0045] According to some embodiments, step (c) further comprises further isolating the hydrogen from the inert gas and optionally water vapor flown through the first gas outlet.

[0046] According to some embodiments, the further hydrogen isolation comprises condensing the inert gas and optionally water vapor and recovering the hydrogen gas.

[0047] According to some embodiments, step (d) is performed substantially in the absence of water.

[0048] According to some embodiments, step (d) is performed under inert gas.

[0049] According to some embodiments, step (d) is performed at a pressure Pdin the range of 0.9 Bar to 2 Bar.

[0050] According to some embodiments, step Tdis in the range of 200°C to 450°C. According to some embodiments, step Tdis in the range of 300°C to 450°C. According to some embodiments, step Tdis in the range of 320°C to 400°C.

[0051] According to some embodiments, step (b) comprises: providing a reactor comprising: a first reaction chamber, which contains the alkali metal and comprises a first gas inlet and a first gas outlet; a first gas inlet valve, configured to monitor gas flow through the first gas inlet into the first reaction chamber, and a first gas outlet valve, configured to monitor fluid flow through the first gas outlet out of the first reaction chamber; flowing the gas mixture through the first gas inlet into the first reaction, wherein the first gas inlet valve is in an open state, thereby contacting the water with the alkali metal and forming the hydrogen and the mixture of the excess alkali metal and alkali metal hydroxide; and step (d) comprises switching the first gas inlet valve to a closed state; andadjusting the temperature of the mixture of step (b) to the temperature Td, thereby forming hydrogen and the alkali metal oxide.

[0052] According to some embodiments, the process comprises step (c) of: flowing the hydrogen formed in step (b), the inert gas and optionally water vapor through the first gas outlet, wherein the first gas outlet valve is in an open state, thereby isolating the hydrogen produced in step (b) from the mixture of the alkali metal and alkali metal hydroxide, which remains within the first reaction chamber.

[0053] According to some embodiments, step (e) comprises flowing the hydrogen formed in step (d) and optionally, the hydrogen produced in step (b) through the first gas outlet, wherein the first gas outlet valve is in an open state, thereby isolating the hydrogen produced in step (d) and optionally, the hydrogen produced in step (b) from the alkali metal oxide, which remains within the first reaction chamber.

[0054] According to some embodiments, step (e) further comprises further isolating the hydrogen from residual inert gas and optionally water vapor. According to some embodiments, the further hydrogen isolation comprises condensing the inert gas and optionally water vapor and recovering the hydrogen gas.

[0055] According to some embodiments, step (f) is performed substantially in the absence of water and hydrogen.

[0056] According to some embodiments, step (f) is performed under vacuum.

[0057] According to some embodiments, step (f) is performed at a pressure Pfin the range of 0.1 torr to 5 torr.

[0058] According to some embodiments, temperature Tf, is in the range of 500°C to 600°C.

[0059] According to some embodiments, the first reaction chamber further comprises a first intermediate opening and a first vacuum opening, and the reactor further comprises: a second reaction chamber, which comprises a second gas inlet, a second gas outlet a second intermediate opening and a second vacuum opening;a second gas inlet valve, configured to monitor gas flow through the second gas inlet into the first reaction chamber, and a second gas outlet valve, configured to monitor gas flow through the second gas outlet out of the second reaction chamber; an intermediate tube connecting the first intermediate opening and the second intermediate opening; and an intermediate tube valve, configured to monitor fluid flow through the intermediate tube; wherein step (f) comprises: switching each of the first gas inlet valve and second gas inlet valve to a closed state; switching the intermediate tube valve to an open state to form fluid communication between the first reaction chamber and the second reaction chamber; connecting the second vacuum opening to a second vacuum source; applying vacuum using the second vacuum source, so that the pressure within the first reaction chamber and second reaction chamber, Pf, is in the range of 0.1 torr to 100 torr; and adjusting the first reaction chamber to temperature Tfto induce the decomposition.

[0060] According to some embodiments, step (g) comprises isolating the recycled alkali metal produced in step (f) by vacuum distillation.

[0061] According to some embodiments, step (g) is performed at a pressure Pgin the range of 0.1 torr to 5 torr.

[0062] According to some embodiments, step (g) comprises adjusting the first reaction chamber to temperature Tgl; adjusting the second reaction chamber to temperature Tg2, which is at least 100°C lower than Tgl; andapplying vacuum using the second vacuum source, so that the pressure within the first reaction chamber and second reaction chamber, Pg, is in the range of 0.5 torr to 5 torr, wherein the alkali metal is solid or liquid at Tg2and Pgand at least partially vaporizes at Tgland Pg, thereby vacuum distilling the alkali metal and condensing it in the second reaction chamber.

[0063] According to some embodiments, Pgis substantially equal to Pf, and wherein steps (g) and (f) are performed simultaneously.

[0064] According to some embodiments, temperature Tgl, is in the range of 500°C to 600°C. According to some embodiments, temperature Tgl, is in the range of 500°C to 1000°C.

[0065] According to some embodiments, temperature Tg2, is in the range of 5°C to 40°C.

[0066] According to some embodiments, adjusting the temperature in each one of steps (d) and (f) comprises applying induction heating.

[0067] According to some embodiments, repeating steps (a) to (g) at least once comprises:(a2) providing an additional gas mixture comprising water vapor and an inert gas;(b2) flowing the additional gas mixture through the second gas inlet into the second reaction chamber, thereby contacting the water with the recycled alkali metal and forming hydrogen and a mixture of the excess alkali metal and alkali metal hydroxide;(c2) optionally, flowing the hydrogen formed in step (b2), the inert gas and optionally water vapor through the second gas outlet, thereby isolating the hydrogen produced in step (b2) from the mixture of the alkali metal and alkali metal hydroxide;(d2) switching the second gas inlet valve to a closed state and adjusting the temperature of the mixture of step (b2) to the temperature Td,induce a reaction between the alkali metal and alkali metal hydroxide, thereby forming hydrogen and the alkali metal oxide;(e2) flowing the hydrogen formed in step (d2) and optionally, the hydrogen produced in step (b2) through the second gas outlet, wherein the second gas outlet valve is in an open state, thereby isolating the hydrogen produced in step (d2) and optionally, the hydrogen produced in step (b2) from the alkali metal oxide, which remains within the second reaction chamber.(f2) switching each of the first gas inlet valve and second gas inlet valve to a closed state, switching the intermediate tube valve to an open state to form fluid communication between the first reaction chamber and the second reaction chamber; connecting the first vacuum opening to a first vacuum source; applying vacuum using the first vacuum source, so that the pressure within the first reaction chamber and second reaction chamber, Pf, is in the range of 0.1 torr to 100 torr; and adjusting the second reaction chamber to temperature Tfto induce decomposition of the alkali metal oxide into a recycled alkali metal and oxygen;(g2) adjusting the first reaction chamber to the temperature Tg2and the second reaction chamber to the temperature Tgl; and applying vacuum using the first vacuum source, so that the pressure within the first reaction chamber and second reaction chamber, Pg, is in the range of 0.5 torr to 5 torr, thereby vacuum distilling the alkali metal and condensing it in the first reaction chamber.

[0068] Further embodiments and the full scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples,while indicating preferred embodiments of the invention, are given by way of illustration only, since 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.

[0069] In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the figures and by study of the following detailed descriptions.BRIEF DESCRIPTION OF THE FIGURES

[0070] The accompanying figures, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention wherein:

[0071] Figure 1 is a reaction cycle diagram representing the reaction steps (b), (d) and (f) of the present invention, using sodium, as an alkali metal and argon as the inert gas, according to some embodiments.

[0072] Figure 2 is a schematic representation of a reaction system configured to carry out the process of the present invention, according to some embodiments.

[0073] Figure 3 is a block diagram representing the process of the present invention, using sodium as an alkali metal, wherein steps (a), (b) and (d) are performed at 1 Bar each, according to some embodiments

[0074] Figures 4A-H collectively represent steps of the present process, according to some embodiments. Figure 4A represents steps (a), (b) and (c) of the present process, using sodium as an alkali metal, according to some embodiments. Figure 4B represents steps (d) and (e) of the present process, using sodium as an alkali metal (sodium hydroxide as the alkali metal hydroxide), according to some embodiments. Figure 4C represents step (f) of the present process, using sodium as an alkali metal (sodium oxide as the alkali metal oxide), according to some embodiments. Figure 4D represents step (g) of the present process, using sodium as an alkali metal, according to some embodiments. Figure 4E represents steps (a2), (b2) and (c2) of the present process, using sodium as an alkali metal, according to some embodiments. Figure 4F represents steps (d2) and (e2) of the present process, using sodium as an alkali metal (sodiumhydroxide as the alkali metal hydroxide), according to some embodiments. Figure 4G represents step (f2) of the present process, using sodium as an alkali metal (sodium oxide as the alkali metal oxide), according to some embodiments. Figure 4H represents step (g2) of the present process, using sodium as an alkali metal, according to some embodiments.DETAILED DESCRIPTION

[0075] In the following description, various aspects of the disclosure will be described. For the purpose of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the different aspects of the disclosure. However, it will also be apparent to one skilled in the art that the disclosure may be practiced without specific details being presented herein. Furthermore, well- known features may be omitted or simplified in order not to obscure the disclosure.

[0076] Before the present disclosure is described in greater detail, it is to be understood that this disclosure is not limited to particular embodiments described, and as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present disclosure will be limited only by the appended claims.

[0077] According to some embodiments, there is provided a process for the splitting of water. According to some embodiments, the process comprises steps (a) to (g) as described herein and repeating steps (a) to (g) at least once, by reusing the alkali metal, which is produced through the process.

[0078] Thus, according to some embodiments, the process comprises:(a) providing a gas mixture comprising water vapor and an inert gas;(b) contacting the gas mixture with an alkali metal, to form hydrogen and a mixture of the alkali metal (MA) and alkali metal hydroxide (MA0H);(c) optionally, isolating the hydrogen produced in step (b) from the mixture of the alkali metal and alkali metal hydroxide;(d) adjusting the temperature of the mixture of step (b) to a temperature Td, which is in the range of 200°C to 450°C to induce a reaction between the alkali metal and alkali metal hydroxide, thereby forming hydrogen and an alkali metal oxide (MA2O);(e) isolating the hydrogen produced in step (d), and optionally, the hydrogen produced in step (b) from the alkali metal oxide;(f) adjusting the alkali metal oxide formed in step (e) to a temperature Tf, which is in the range of 400°C to 1000°C and a pressure Pfin the range of 0.1 torr to 100 torr, to induce a decomposition of the alkali metal oxide into a recycled alkali metal and oxygen;(g) isolating the recycled alkali metal produced in step (f), wherein the process further comprises repeating steps (a) to (g) at least once, by reusing the recycled alkali metal isolated in step (f) for subsequent use in repeated step (b).

[0079] According to some embodiments, the process comprises:(a) providing a gas mixture comprising water vapor and an inert gas;(b) contacting the gas mixture with an alkali metal, to form hydrogen and a mixture of the alkali metal (MA) and alkali metal hydroxide (MA0H);(c) optionally, isolating the hydrogen produced in step (b) from the mixture of the alkali metal and alkali metal hydroxide;(d) adjusting the temperature of the mixture of step (b) to a temperature Td, which is in the range of 200°C to 450°C to induce a reaction between the alkali metal and alkali metal hydroxide, thereby forming hydrogen and an alkali metal oxide (MA2O);(e) isolating the hydrogen produced in step (d), and optionally, the hydrogen produced in step (b) from the alkali metal oxide;(f) adjusting the alkali metal oxide formed in step (e) to a temperature Tf, which is in the range of 400°C to 1000°C and a pressure sub-atmospheric Pf, to induce a decomposition of the alkali metal oxide into a recycled alkali metal and oxygen;(g) isolating the recycled alkali metal produced in step (f), wherein the process further comprises repeating steps (a) to (g) at least once, by reusing the recycled alkali metal isolated in step (f) for subsequent use in repeated step (b).

[0080] Specific reference is now made to Figure 1, which is a reaction cycle diagram 1000 representing specific embodiments of the present invention, using sodium as an alkali metal and argon as inert gas, according to some embodiments.

[0081] According to some embodiments, the alkali metal (MA) is sodium. According to some embodiments, the inert gas comprises argon.

[0082] As shown in Figure 1, indicator 1010, a gas mixture comprising water vapor and argon is provided in step (a) of the present process, according to some embodiments. The specifics of step (a) are detailed below.

[0083] As shown by indicator 1030, the water vapor portion of the gas mixture 1010 is contacting sodium metal 1020 to form a reaction as represented below:as described herein with respect to step (b) of the present process, the specifics of which are detailed below. According to some embodiments, this step is responsible for producing hydrogen, as reflected by indicator 1040.

[0084] Also can be appreciated from indicator 1040 is that the inert argon gas does not react with the sodium, and is released together with the hydrogen gas, according to some embodiments. Specifically, indicator 1040 relates to step (c) of the present process of isolating the hydrogen produced in step (b) from the mixture of the sodium metal and sodium hydroxide, according to some embodiments. As can be further appreciated, Figure 1 represents an embodiment, wherein the hydrogen is isolated together with the inert gas from the mixture of the sodium metal and sodium hydroxide. However, according to some embodiments, the present invention contemplates further isolation of hydrogen from the inert gas.

[0085] With reference to indicator 1050, the water vapor is added in an amount, so that the sodium is not consumed, i.e., the sodium is in excess, therefore a mixture of sodium metal and sodium hydroxide 1050 remains, according to some embodiments.

[0086] As further shown by indicator 1060, under conditions specified herein, the sodium, which was in excess over the water in step (b) is further reacted with the sodium hydroxide formed in step (b), according to the reaction scheme represented below:as described herein with respect to step (d) of the present process, the specifics of which are detailed below. According to some embodiments, the reaction scheme is as represented below, wherein the sodium is in a molar excess over the sodium hydroxide.wherein d is greater than c;

[0087] Indicator 1070 points at the sodium oxide produced in step (d).

[0088] Indicator 1080 represents step (e), which is directed to the isolation of hydrogen. As discussed with respect to step (c) and indicator 1040, Figure 1 represents an embodiment, wherein the hydrogen is isolated together with the inert gas from the mixture of the sodium metal and sodium hydroxide. However, according to some embodiments, the present invention contemplates further isolation of hydrogen from the inert gas.

[0089] As shown by indicator 1090, under conditions specified herein, the sodium oxide is further decomposed to form oxygen 1100, and recycled sodium 1020, according to the reaction scheme represented below:as described herein with respect to step (f) of the present process, the specifics of which are detailed below.

[0090] Specific reference is now made to Figure 2, which is a schematic representation of a reaction system 100, configured to carry out the process of the present invention, according to some embodiments.

[0091] According to some embodiments, reaction system 100 comprises a water source 102. According to some embodiments, the water source 102 comprises a water container. According to some embodiments, the water container 102 contains water. According to some embodiments, the water container 102 contains an aqueous composition. According to some embodiments, the aqueous composition is an aqueous solution. According to some embodiments, the aqueous composition is aqueous salt composition. According to some embodiments, the aqueous salt composition is a saturated aqueous salt composition. According to some embodiments, the aqueous solution is aqueous salt composition. According to some embodiments, the aqueous salt solution is a saturated aqueous salt composition. According to some embodiments, the salt is selected from the group consisting of: ammonium nitrate, ammonium sulfate, magnesium chloride, magnesium nitrate, lithium chloride, potassium sulfate, potassium nitrate, potassium chloride, potassium acetate, potassium hydroxide, sodium chloride, sodium nitrite, sodium dichromate and combinations thereof. Each possibility represents a separate embodiment of the invention. According to some embodiments, the water source 102 comprises a heater (not shown) configured to elevate the temperature of the contents of the water source 102.

[0092] The term "solution" as used herein broadly refers to a combination, mixture and / or admixture of ingredients having at least one liquid component. Thus, the term "aqueous solution" refers to any solution, in which its major liquid component is water. Aqueous solutions typically include water in greater quantity or volume than a solute. Preferably, "solution" refers broadly to a mixture of miscible substances, where one substance dissolves in a second substance. More preferably, in a solution the essential components are homogeneously mixed and that the components are subdivided to such an extent that there is no appearance of light scattering visible to the naked eye when a one-inch diameter bottle of the mixture is viewed in sunlight. The term “salt solution” refer to an aqueous solution of one or more salts. The term “saturated salt solution” means an aqueous solution that contains a maximum concentration of a particular dissolved salt and in which no additional amount of the particular salt can be dissolved. The maximum amount of dissolved salt in a saturated salt solution may be dependent on the temperature of the solution and the chemical identity of the salt. According to some embodiments, a saturated salt solution corresponds to a saturated roomtemperature salt solution. Saturated solutions may, for example, include a precipitated amount of salt.

[0093] According to some embodiments, the reaction system 100 comprises an inert gas source 104. According to some embodiments, the inert gas source 104 is an inert gas source cylinder 104. According to some embodiments, the inert gas source 104 is a nitrogen cylinder 104. According to some embodiments, the inert gas source 104 is an argon cylinder 104. According to some embodiments, the inert gas source contains an inert gas. According to some embodiments, the inert gas is nitrogen or argon. Each possibility represents a separate embodiment of the invention.

[0094] According to some embodiments, the inert gas source 104 is connect to a tube at an outflow end of the tube. According to some embodiments, an inflow end of the tube is located in the water source 102. According to some embodiments, the inflow end of the tube is located in or over a surface of the aqueous composition contained within the water source 102. According to some embodiments, the tube enables inert gas flow from the inert gas source 104 to the water source 102. According to some embodiments, upon flowing inert gas from the inert gas source 104 a gas mixture forms, the gas mixture comprises water vapor and the inert gas.

[0095] According to some embodiments, the reaction system 100 comprises a first gas mixture inlet tube 106. According to some embodiments, the gas mixture inlet tube 106 comprises an inflow end connected to the water source 102. According to some embodiments, the first gas mixture inlet tube 106 comprises an outflow end connected to first reaction chamber 150. First reaction chamber 150 is presented and discussed below. According to some embodiments, the first gas mixture inlet tube 106 is configured to enable fluid communication between the water source 102 and the first reaction chamber 150.

[0096] According to some embodiments, reaction system 100 comprises a first reaction chamber 150. According to some embodiments, the first reaction chamber 150 is an enclosed chamber.

[0097] As used herein, the terms "closed reaction chamber" and "enclosed reaction chamber" refers to a closed system which at least temporarily isolates reaction media contained therein from the surrounding environment. It is to be understood that closed chambers may include opening(s) and / or a cover, for gaining access to their contents,and are not limited to permanently sealed or closed structures. Elements, such as a cover or a port may provide reversible access to the interior of the chamber, such that its closed feature may be limited to the operation period thereof (e.g. the reaction and / or isolation periods).

[0098] According to some embodiments, the first reaction chamber 150 is stable at temperatures in the range of 500°C to 1100°C. According to some embodiments, the first reaction chamber 150 is stable towards alkali metals. According to some embodiments, the first reaction chamber 150 is stable towards sodium metal. According to some embodiments, the first reaction chamber 150 is stable towards application of pressures in the range of 0.001 Bar to 10 Bar. According to some embodiments, the first reaction chamber 150 is stable towards sodium metal at temperatures in the range of 500°C to 1100°C and pressures in the range of 0.0001 Bar to 10 Bar.

[0099] It is to be understood that the reaction chamber stability, as manifested in the present invention relates to the reaction chamber material not reacting, decomposing or degrading substantially upon application of extreme conditions as specified herein.

[0100] According to some embodiments, the first reaction chamber 150 comprises a first gas mixture inlet 152 configured to allow access of fluids into and / or out of the first reaction chamber 150. According to some embodiments, the first gas mixture inlet 152 is configured to allow access of fluids into the first reaction chamber 150. According to some embodiments, the first gas mixture inlet 152 is configured to allow access of gas into the first reaction chamber 150.

[0101] According to some embodiments, first gas mixture inlet 152 is connected to the first gas mixture inlet tube 106. According to some embodiments, the first gas mixture inlet tube 106 is positioned such that generation of the gas mixture in the water source 102 may result in the flow of the gas mixture through the gas mixture inlet tube 106 into the first reaction chamber 150.

[0102] According to some embodiments, the reaction system 100 comprises a gas mixture inlet valve 110 configured to monitor gas flow through the gas mixture inlet tube 106.

[0103] According to some embodiments, the reaction system 100 comprises a first gas inlet valve 112. According to some embodiments, the first gas inlet valve 112 isconfigured to monitor gas flow through the first gas inlet 152 into the first reaction chamber 150.

[0104] According to some embodiments, the reaction system 100 comprises a first heater 116. According to some embodiments, the first heater 116 is configured to elevate the temperature of the first reaction chamber 150 to at least 200°C. According to some embodiments, the first heater 116 is configured to elevate the temperature of the first reaction chamber 150 to at least 300°C. According to some embodiments, the first heater 116 is configured to elevate the temperature of the first reaction chamber 150 to at least 400°C. According to some embodiments, the first heater 116 is configured to elevate the temperature of the first reaction chamber 150 to at least 500°C. According to some embodiments, the first heater 116 is configured to elevate the temperature of the first reaction chamber 150 to at least 550°C. According to some embodiments, the first heater 116 is configured to elevate the temperature of the first reaction chamber 150 to a temperature in the range of 500°C to 1500°C.

[0105] According to some embodiments, the first heater 116 comprises an induction heater. According to some embodiments, the first heater 116 is an induction heater.

[0106] According to some embodiments, the first heater 116 is positioned in the vicinity of the first reaction chamber 150.

[0107] According to some embodiments, the reaction system 100 comprises a first detector 120. According to some embodiments, the first detector 120 comprises an alkali metal detector, alkali metal hydroxide detector, alkali metal oxide detector or a combination thereof. Each possibility represents a separate embodiment of the invention. According to some embodiments, the first detector 120 is configured to quantify the amount of alkali metal, alkali metal hydroxide, alkali metal oxide or a combination thereof within the first reaction chamber 150.

[0108] According to some embodiments, the first reaction chamber 150 comprises a first gas outlet 154. According to some embodiments, the first gas outlet 154 is configured to allow access of fluids into and / or out of the first reaction chamber 150. According to some embodiments, the first gas outlet 154 is configured to allow exit of fluids out of the first reaction chamber 150. According to some embodiments, the first gas outlet 154 is configured to allow exit of gas out of the first reaction chamber 150.

[0109] According to some embodiments, the reaction system 100 comprises a first gas outlet tube 124. According to some embodiments, the first gas outlet tube 124 comprises an inflow end connected to first reaction chamber 150. According to some embodiments, the first gas outlet tube 124 comprises an inflow end connected to the first gas outlet 154. According to some embodiments, the first gas outlet tube 124 comprises an outflow end connected to a gas separation unit 148. The gas separation unit 148 is discussed hereinbelow. According to some embodiments, the first gas outlet tube 124 is configured to enable fluid communication between the gas separation unit 148 and the first reaction chamber 150.

[0110] According to some embodiments, the first gas outlet 154 is connected to the first gas outlet tube 124. According to some embodiments, the first gas outlet tube 124 is positioned such that generation of gas (e.g., hydrogen) in the first reaction chamber 150 will result in the flow of the gas through the first gas outlet tube 124 from the first reaction chamber 150 to the gas separation unit 148.

[0111] According to some embodiments, the reaction system 100 comprises a first gas outlet valve 128. According to some embodiments, the first gas outlet valve 128 is configured to monitor gas flow through the first gas outlet 154 out of the first reaction chamber 150.

[0112] According to some embodiments, the first reaction chamber 150 comprises a first intermediate opening 156. According to some embodiments, the first intermediate opening 156 is configured to allow access of fluids into and / or out of the first reaction chamber 150. According to some embodiments, the first intermediate opening 156 is configured to allow exit of fluids out of the first reaction chamber 150. According to some embodiments, the first intermediate opening 156 is configured to allow entry of fluids into the first reaction chamber 150. According to some embodiments, the first intermediate opening 156 is configured to allow exit of fluids out of the first reaction chamber 150 and to allow entry of fluids into the first reaction chamber 150. According to some embodiments, the first intermediate opening 156 is configured to allow exit of fluids out of the first reaction chamber 150 and to allow entry of gas into the first reaction chamber 150 under vacuum.

[0113] According to some embodiments, the reaction system 100 comprises an intermediate tube 132. According to some embodiments, the intermediate tube 132 is avacuum tube. According to some embodiments, the intermediate tube 132 is a vacuum tube configured to withstand low pressure of 1 torr. According to some embodiments, the intermediate tube 132 is chemically resistant towards alkali metals. According to some embodiments, the intermediate tube 132 is chemically resistant towards sodium vapor. According to some embodiments, the intermediate tube 132 comprises a first end connected to first reaction chamber 150. According to some embodiments, the intermediate tube 132 comprises a first end connected to the first intermediate opening 156. According to some embodiments, the intermediate tube 132 comprises a second end connected to a second reaction chamber 170. The second reaction chamber 170 is discussed hereinbelow. According to some embodiments, the intermediate tube 132 is configured to enable fluid communication between the second reaction chamber 170 and the first reaction chamber 150.

[0114] According to some embodiments, the intermediate opening 156 is connected to the intermediate tube 132. According to some embodiments, the intermediate tube 132 is positioned such that upon application of vacuum to its second end suction will be applied to the first reaction chamber 150. According to some embodiments, the intermediate tube 132 is positioned such that upon application of vacuum to its first end suction will be applied to the second reaction chamber 170.

[0115] According to some embodiments, the reaction system 100 comprises an intermediate tube valve 134. According to some embodiments, the intermediate tube valve 134 is configured to monitor gas flow through the intermediate tube 132 between the first reaction chamber 150 and the second reaction chamber 170. According to some embodiments, the intermediate tube valve 134 is configured to monitor vacuum within the intermediate tube 132.

[0116] According to some embodiments, the first reaction chamber 150 comprises a first vacuum opening 158. According to some embodiments, the first vacuum opening 158 is configured to allow access of fluids into and / or out of the first reaction chamber 150. According to some embodiments, the first vacuum opening 158 is configured to allow exit of fluids out of the first reaction chamber 150. According to some embodiments, the first vacuum opening 158 is configured to allow exit of gas out of the first reaction chamber 150. According to some embodiments, the first vacuum opening158 is configured to allow application of vacuum therethrough on the first reaction chamber 150.

[0117] According to some embodiments, the reaction system 100 comprises a first vacuum tube 136. According to some embodiments, the first vacuum tube 136 comprises an inflow end connected to first reaction chamber 150. According to some embodiments, the first vacuum tube 136 comprises an inflow end connected to the first vacuum opening 158. According to some embodiments, the first vacuum tube 136 comprises an outflow end connected to a first vacuum source 144. The first vacuum source 144 is discussed hereinbelow. According to some embodiments, the first vacuum tube 136 is configured to enable fluid communication between the first vacuum source 144 and the first reaction chamber 150. According to some embodiments, the first vacuum tube 136 is configured to allow application of vacuum therethrough on the first reaction chamber 150.

[0118] According to some embodiments, the first vacuum opening 158 is connected to the first vacuum tube 136. According to some embodiments, the first vacuum tube 136 is positioned such that application of vacuum by the first vacuum source 144 will result in suction to the first reaction chamber 150 through the first vacuum tube 136.

[0119] According to some embodiments, the reaction system 100 comprises a first vacuum valve 140. According to some embodiments, the first vacuum valve 140 is configured to monitor vacuum through the first vacuum tube 136.

[0120] According to some embodiments, the reaction system 100 comprises a first vacuum source 144. According to some embodiments, the first vacuum source 144 comprises a vacuum pump. According to some embodiments, the first vacuum source 144 is a vacuum pump. According to some embodiments, the first vacuum source 144 is configured to generate vacuum in the range of 0.1 torr to 100 torr, including each value and sub-range within the specified range.

[0121] According to some embodiments, the reaction system 100 comprises a second gas mixture inlet tube 108. According to some embodiments, the second gas mixture inlet tube 108 comprises an inflow end connected to the water source 102. According to some embodiments, the second gas mixture inlet tube 108 comprises an outflow end connected to second reaction chamber 170. The second reaction chamber 170 is presented and discussed below. According to some embodiments, the second gasmixture inlet tube 108 is configured to enable fluid communication between the water source 102 and the second reaction chamber 170.

[0122] According to some embodiments, reaction system 100 comprises a second reaction chamber 170. According to some embodiments, the second reaction chamber 170 is an enclosed chamber. The term "enclosed reaction chamber" is described hereinabove.

[0123] According to some embodiments, the second reaction chamber 170is stable at temperatures in the range of 500°C to 1000°C. According to some embodiments, the second reaction chamber 170 is stable towards alkali metals. According to some embodiments, the second reaction chamber 170 is stable towards sodium metal. According to some embodiments, the second reaction chamber 170 is stable towards application of pressures in the range of 0.0001 Bar to 10 Bar. According to some embodiments, the second reaction chamber 170 is stable towards sodium metal at temperatures in the range of 500°C to 1000°C and pressures in the range of 0.0001 Bar to 10 Bar.

[0124] According to some embodiments, the second reaction chamber 170 comprises a second gas mixture inlet 172 configured to allow access of fluids into and / or out of the second reaction chamber 170. According to some embodiments, the second gas mixture inlet 172 is configured to allow access of fluids into the second reaction chamber 170. According to some embodiments, the second gas mixture inlet 172 is configured to allow access of gas into the second reaction chamber 170.

[0125] According to some embodiments, the second gas mixture inlet 172 is connected to the second gas mixture inlet tube 108. According to some embodiments, the second gas mixture inlet tube 108 is positioned such that generation of the gas mixture in the water source 102 may result in the flow of the gas mixture through the second gas mixture inlet tube 108 into the second reaction chamber 170.

[0126] According to some embodiments, the gas mixture inlet valve 110 is further configured to monitor gas flow through the second gas mixture inlet tube 108. Alternatively, according to some embodiments, a separate gas mixture inlet valve (not shown) is configured to monitor gas flow through the second gas mixture inlet tube 108.

[0127] According to some embodiments, the reaction system 100 comprises second first gas inlet valve 114. According to some embodiments, the second first gas inlet valve 114 is configured to monitor gas flow through the second gas mixture inlet 172 into the second reaction chamber 170.

[0128] According to some embodiments, the reaction system 100 comprises a second heater 118. According to some embodiments, the second heater 118 is configured to elevate the temperature of the second reaction chamber 170 to at least 200°C. According to some embodiments, the second heater 118 is configured to elevate the temperature of the second reaction chamber 170 to at least 300°C. According to some embodiments, the second heater 118 is configured to elevate the temperature of the second reaction chamber 170 to at least 400°C. According to some embodiments, the second heater 118 is configured to elevate the temperature of the second reaction chamber 170 to at least 500°C. According to some embodiments, the second heater 118 is configured to elevate the temperature of the second reaction chamber 170 to at least 550°C. According to some embodiments, the second heater 118 is configured to elevate the temperature of the second reaction chamber 170 to a temperature in the range of 500°C to 1500°C.

[0129] According to some embodiments, the second heater 118 comprises an induction heater. According to some embodiments, the second heater 118 is an induction heater.

[0130] According to some embodiments, the second heater 118 is positioned in the vicinity of the second reaction chamber 170.

[0131] According to some embodiments, the reaction system 100 comprises a second detector 122. According to some embodiments, the second detector 122 comprises an alkali metal detector, alkali metal hydroxide detector, alkali metal oxide detector or a combination thereof. Each possibility represents a separate embodiment of the invention. According to some embodiments, the second detector 122 is configured to quantify the amount of alkali metal, alkali metal hydroxide, alkali metal oxide or a combination thereof within the second reaction chamber 170.

[0132] According to some embodiments, the second reaction chamber 170 comprises a second gas outlet 174. According to some embodiments, the second gas outlet 174 is configured to allow access of fluids into and / or out of the second reactionchamber 170. According to some embodiments, the second gas outlet 174 is configured to allow exit of fluids out of the second reaction chamber 170. According to some embodiments, the second gas outlet 174 is configured to allow exit of gas out of the second reaction chamber 170.

[0133] According to some embodiments, the reaction system 100 comprises a second gas outlet tube 126. According to some embodiments, the second gas outlet tube 126 comprises an inflow end connected to second reaction chamber 170. According to some embodiments, the second gas outlet tube 126 comprises an inflow end connected to the second gas outlet 174. According to some embodiments, the second gas outlet tube 126 comprises an outflow end connected to the gas separation unit 148. The gas separation unit 148 is discussed hereinbelow. According to some embodiments, the second gas outlet tube 126 is configured to enable fluid communication between the gas separation unit 148 and the second reaction chamber 170.

[0134] According to some embodiments, the second gas outlet 174 is connected to the second gas outlet tube 126. According to some embodiments, the second gas outlet tube 126 is positioned such that generation of gas (e.g., hydrogen) in the second reaction chamber 170 will result in the flow of the gas through the second gas outlet tube 126 from the second reaction chamber 170 to the gas separation unit 148.

[0135] According to some embodiments, the reaction system 100 comprises a second gas outlet valve 130. According to some embodiments, the second gas outlet valve 130is configured to monitor gas flow through the second gas outlet 174 out of the second reaction chamber 170.

[0136] According to some embodiments, the first reaction chamber 150 comprises a second intermediate opening 176. According to some embodiments, the second intermediate opening 176 is configured to allow access of fluids into and / or out of the second reaction chamber 170. According to some embodiments, the second intermediate opening 176 is configured to allow exit of fluids out of the second reaction chamber 170. According to some embodiments, the second intermediate opening 176 is configured to allow entry of fluids into the second reaction chamber 170. According to some embodiments, the second intermediate opening 176 is configured to allow exit of fluids out of the second reaction chamber 170 and to allow entry of fluids into the second reaction chamber 170. According to some embodiments, second intermediateopening 176 is configured to allow exit of fluids out of the second reaction chamber170 and to allow entry of gas into the second reaction chamber 170 under vacuum.

[0137] According to some embodiments, the intermediate tube 132 comprises a second end connected to the second reaction chamber 170. According to some embodiments, the intermediate tube 132 comprises a second end connected to the second intermediate opening 176. According to some embodiments, the intermediate tube 132 is configured to enable fluid communication between the second reaction chamber 170 and the first reaction chamber 150. According to some embodiments, the intermediate tube 132 is configured to enable vacuum communication between the second reaction chamber 170 and the first reaction chamber 150.

[0138] According to some embodiments, the second intermediate opening 176 is connected to the intermediate tube 132.

[0139] According to some embodiments, the second reaction chamber 170 comprises a second vacuum opening 178. According to some embodiments, the second vacuum opening 178 is configured to allow access of fluids into and / or out of the second reaction chamber 170. According to some embodiments, the second vacuum opening 178 is configured to allow exit of fluids out of the second reaction chamber 170. According to some embodiments, the second vacuum opening 178 is configured to allow exit of gas out of the second reaction chamber 170. According to some embodiments, the second vacuum opening 178 is configured to allow application of vacuum therethrough on the second reaction chamber 170.

[0140] According to some embodiments, the reaction system 100 comprises a second vacuum tube 138. According to some embodiments, the second vacuum tube 138 comprises an inflow end connected to second reaction chamber 170. According to some embodiments, the second vacuum tube 138 comprises an inflow end connected to the second vacuum opening 178. According to some embodiments, the second vacuum tube 138 comprises an outflow end connected to a second vacuum source 146. The second vacuum source 146 is discussed hereinbelow. According to some embodiments, the second vacuum tube 138 is configured to enable fluid communication between the second vacuum source 146 and the second reaction chamber 170. According to some embodiments, the second vacuum tube 138 is configured to allow application of vacuum therethrough on the second reaction chamber 170.

[0141] According to some embodiments, the second vacuum opening 178 is connected to the second vacuum tube 138. According to some embodiments, the second vacuum tube 138 is positioned such that application of vacuum by the second vacuum source 146 will result in suction to the second reaction chamber 170 through the second vacuum tube 138.

[0142] According to some embodiments, the reaction system 100 comprises a second vacuum valve 142. According to some embodiments, the second vacuum valve 142 is configured to monitor vacuum through the second vacuum tube 138.

[0143] According to some embodiments, the reaction system 100 comprises a second vacuum source 146. According to some embodiments, the second vacuum source 146 comprises a vacuum pump. According to some embodiments, the second vacuum source 146 is a vacuum pump. According to some embodiments, the second vacuum source 146 is configured to generate vacuum in the range of 0.1 torr to 100 torr, including each value and sub-range within the specified range.

[0144] According to some embodiments, the reaction system 100 further comprises a gas separation unit 148. According to some embodiments, the gas separation unit 148 is configured to separate individual gas components from a gas mixture. According to some embodiments, the gas separation unit 148 is configured to separate to separate hydrogen from inert gasses. According to some embodiments, the gas separation unit 148 is configured to separate to separate hydrogen from nitrogen. According to some embodiments, the gas separation unit 148 is configured to separate to separate hydrogen from argon. According to some embodiments, the gas separation unit 148 is configured to separate to separate hydrogen from water vapor. According to some embodiments, the separation is based on different condensation points of the different gasses, such as, but not limited to, temperature and pressure. Thus, according to some embodiments, the gas separation unit 148 comprises a condenser. According to some embodiments, the gas separation unit 148 comprises a cooling unit, the gas separation unit 148 comprises a pressurization unit.

[0145] According to some embodiments, the reaction system 100 further comprises a hydrogen analyzer 149 configured to analyze and / or quantify hydrogen in gas compositions. The analysis may include, but not limited to, hydrogen purity, hydrogen quantity and the like.

[0146] Specific reference is now made to Figure 3 and Figures 4A to Figure 4H, which represent steps of the present process, according to some embodiments

[0147] According to some embodiments, the process comprises steps (a) to (g) as described herein and repeating steps (a) to (g) at least once, by reusing the alkali metal, which is produced through the process.

[0148] Specific reference is now made to step (a) of the present process. According to some embodiments, the present process comprises step (a) of providing a gas mixture.

[0149] According to some embodiments, the gas mixture provided in step (a) comprises water vapor and an inert gas. According to some embodiments, the gas mixture consists essentially of water vapor and an inert gas. The term “consist essentially of’ as used in the context of the present embodiment is intended to cover gas mixtures, in which water vapor is the main reactive gas constituent and the inert gas is the main non-reactive gas constituent, with respect to the reaction of step (b).

[0150] According to some embodiments, the gas mixture comprises at least 30% v / v total volume of water vapor and inert gas of the total volume of the gas mixture. According to some embodiments, the gas mixture comprises at least 80% v / v total volume of water vapor and inert gas of the total volume of the gas mixture. According to some embodiments, the gas mixture comprises at least 85% v / v total volume of water vapor and inert gas of the total volume of the gas mixture. According to some embodiments, the gas mixture comprises at least 90% v / v total volume of water vapor and inert gas of the total volume of the gas mixture. According to some embodiments, the gas mixture comprises at least 95% v / v total volume of water vapor and inert gas of the total volume of the gas mixture. According to some embodiments, the gas mixture comprises at least 97% v / v total volume of water vapor and inert gas of the total volume of the gas mixture. According to some embodiments, the gas mixture comprises at least 99% v / v total volume of water vapor and inert gas of the total volume of the gas mixture. According to some embodiments, the gas mixture consists of water vapor and an inert gas.

[0151] According to some embodiments, step (a) comprises providing the inert gas to the gas mixture from the inert gas source 104.

[0152] According to some embodiments, step (a) comprises providing the water vapor to the gas mixture from the water source 102.

[0153] The term “water vapor” as used herein refers to a composition, which comprises water in a gas state, such as, but not limited to, water steam, volatilized water, vaporized water, evaporated water and the like, wherein the vaporization, evaporation and volatilization may be performed by any means known in the art, such as temperature and / or pressure adjustment and flowing gas in or over a water source. It is to be understood that the term “water vapor” also include the humidity naturally formed over liquid water reservoirs (e.g., flowing or standing water).

[0154] According to some embodiments, the gas mixture provided in step (a) is substantially devoid from liquid water.

[0155] The term "substantially devoid” refers to a composition that does not contain a specific substance at a specific state, or substantially does not the specific substance at the specific state. Compositions that substantially do not contain a substance can contain trace amount, such as <5% w / w <3% w / w, <2% w / w. <1% or <0.5% w / w of the substance, according to some embodiments. Each possibility represents a separate embodiment of the invention.

[0156] According to some embodiments, the gas mixture provided in step (a) comprises no more than 2% liquid water w / w. According to some embodiments, the gas mixture provided in step (a) comprises no more than 1% liquid water w / w. According to some embodiments, the gas mixture provided in step (a) comprises no more than 0.5% liquid water w / w. According to some embodiments, the gas mixture provided in step (a) comprises no more than 0.25% liquid water w / w. According to some embodiments, the gas mixture provided in step (a) comprises no more than 0.1% liquid water w / w. According to some embodiments, the gas mixture provided in step (a) is devoid of any detectable amount of liquid water.

[0157] According to some embodiments, the gas mixture provided in step (a) is substantially devoid from water aerosol. According to some embodiments, the gas mixture provided in step (a) comprises no more than 2% water aerosol w / w. According to some embodiments, the gas mixture provided in step (a) comprises no more than 1% water aerosol w / w. According to some embodiments, the gas mixture provided in step (a) comprises no more than 0.5% water aerosol w / w. According to some embodiments,the gas mixture provided in step (a) comprises no more than 0.25% water aerosol w / w. According to some embodiments, the gas mixture provided in step (a) comprises no more than 0.1% water aerosol w / w. According to some embodiments, the gas mixture provided in step (a) is devoid of any detectable amount of water aerosol.

[0158] Without wishing to be bound by any theory of mechanism of action, it was found that provision of water in a gas state enables a controlled reaction with the alkali metal in step (b).

[0159] According to some embodiments, the inert gas comprises argon, helium, nitrogen or a combination thereof. Each possibility represents a separate embodiment of the invention. According to some embodiments, the inert gas comprises argon, nitrogen or both. According to some embodiments, the inert gas comprises argon. According to some embodiments, the inert gas is argon. According to some embodiments, the inert gas comprises nitrogen. According to some embodiments, the inert gas is nitrogen. According to some embodiments, the inert gas comprises nitrogen and argon.

[0160] Although in most commercial processes nitrogen is preferred over argon, as an inert gas, the present invention contemplates recycling of the inert gas, e.g., during step (c) and / or (e), so, according to some embodiments, both are suitable as inert gasses.

[0161] According to some embodiments, the gas mixture of step (a) comprises at least 80% inert gas v / v. According to some embodiments, the gas mixture of step (a) comprises at least 85% inert gas v / v. According to some embodiments, the gas mixture of step (a) comprises at least 90% inert gas v / v. According to some embodiments, the gas mixture of step (a) comprises at least 92% inert gas v / v. According to some embodiments, the gas mixture of step (a) comprises at least 94% inert gas v / v. According to some embodiments, the gas mixture of step (a) comprises at least 96% inert gas v / v. According to some embodiments, the gas mixture of step (a) comprises 90% to 99% inert gas v / v, including each value and sub-range within the specified range.

[0162] According to some embodiments, the gas mixture of step (a) comprises water vapor at a relative humidity of 10% to 100% in the inert gas, including each value and sub-range within the specified range.

[0163] The term “humidity” as used herein, refers to the concentration of water vapor present in gas compositions. Three primary measurements of humidity are widely employed: absolute, relative, and specific. Absolute humidity is expressed as either mass of water vapor per volume of a moist gas composition (in grams per cubic meter) or as mass of water vapor per mass of a dry gas composition (usually in grams per kilogram). Relative humidity, often expressed as a percentage, indicates a present state of absolute humidity relative to a maximum humidity given the same temperature. Specific humidity is the ratio of water vapor mass to total moist air parcel mass.

[0164] The term “relative humidity” (RH) of a gas mixture is defined as the ratio of the partial pressure of water vapor in air to the saturation vapor pressure of water at the same temperature, usually expressed as a percentage:

[0165] RH = P / Ps;

[0166] wherein P is the partial pressure of water vapor and Psis the saturation vapor pressure.

[0167] In other words, relative humidity is the ratio of how much water vapor is in the gas mixture and how much water vapor the air could potentially contain at a given temperature. It varies with the temperature of the air: colder air can hold less vapor. So changing the temperature of air can change the relative humidity, even when the absolute humidity remains constant.

[0168] According to some embodiments, the relative humidity of the water vapor in the gas mixture is in the range of 20% to 100%. According to some embodiments, the relative humidity of the water vapor in the gas mixture is in the range of 30% to 100%. According to some embodiments, the relative humidity of the water vapor in the gas mixture is in the range of 40% to 100%. According to some embodiments, the relative humidity of the water vapor in the gas mixture is in the range of 50% to 100%. According to some embodiments, the relative humidity of the water vapor in the gas mixture is in the range of 60% to 100%. According to some embodiments, the relative humidity of the water vapor in the gas mixture is in the range of 70% to 100%. According to some embodiments, the relative humidity of the water vapor in the gas mixture is at least 10%. According to some embodiments, the relative humidity of the water vapor in the gas mixture is at least 20%. According to some embodiments, the relative humidity of the water vapor in the gas mixture is at least 30%. According tosome embodiments, the relative humidity of the water vapor in the gas mixture is at least 40%. According to some embodiments, the relative humidity of the water vapor in the gas mixture is at least 50%. According to some embodiments, the relative humidity of the water vapor in the gas mixture is no more than 95%. According to some embodiments, the relative humidity of the water vapor in the gas mixture is no more than 90%. According to some embodiments, the relative humidity of the water vapor in the gas mixture is no more than 85%. According to some embodiments, the relative humidity of the water vapor in the gas mixture is no more than 80%.

[0169] According to some embodiments, the gas mixture of step (a) comprises 0.5% to 3.2% water vapor v / v in the inert gas, including each value and sub-range within the specified range. According to some embodiments, the gas mixture of step (a) comprises 1.2% to 3.2% water vapor v / v in the inert gas.

[0170] According to some embodiments, the gas mixture of step (a) comprises at least 0.25% water vapor v / v. According to some embodiments, the gas mixture of step (a) comprises at least 0.5% water vapor v / v. According to some embodiments, the gas mixture of step (a) comprises at least 0.75% water vapor v / v. According to some embodiments, the gas mixture of step (a) comprises at least 1% water vapor v / v. According to some embodiments, the gas mixture of step (a) comprises at least 1.5% water vapor v / v. According to some embodiments, the gas mixture of step (a) comprises at least 2% water vapor v / v. According to some embodiments, the gas mixture of step (a) comprises at least 2.5% water vapor v / v. According to some embodiments, the gas mixture of step (a) comprises at least 3% water vapor v / v.

[0171] According to some embodiments, the gas mixture of step (a) comprises no more than 10% water vapor v / v. According to some embodiments, the gas mixture of step (a) comprises no more than 7.5% water vapor v / v. According to some embodiments, the gas mixture of step (a) comprises no more than 6% water vapor v / v. According to some embodiments, the gas mixture of step (a) comprises no more than 5% water vapor v / v. According to some embodiments, the gas mixture of step (a) comprises no more than 4% water vapor v / v. According to some embodiments, the gas mixture of step (a) comprises no more than 3.5% water vapor v / v.

[0172] It was found that a convenient method to provide a gas mixture, which fulfils the requirements for the present process and also complies with the subsequent processsteps is a humidity control using saturated salt solution. The concept of this method is described in: The Engineering ToolBox (2014). Saturated Salt Solutions and control of Air Humidity, [online] Available at: https: / / www.engineeringtoolbox.com / salt- humidity-d_1887.html.

[0173] According to some embodiments, step (a) comprises providing an aqueous salt solution and flowing an inert gas over or through the aqueous salt solution, thereby forming the gas mixture. According to some embodiments, step (a) comprises providing an aqueous salt solution in the water source 102 and flowing an inert gas from the inert gas source 104 over or through the aqueous salt solution, thereby forming the gas mixture. According to some embodiments, the aqueous salt solution is a saturated aqueous salt solution. According to some embodiments, the salt is selected from the group consisting of: ammonium nitrate, ammonium sulfate, magnesium chloride, magnesium nitrate, lithium chloride, potassium sulfate, potassium nitrate, potassium chloride, potassium acetate, potassium hydroxide, sodium chloride, sodium nitrite, sodium dichromate and combinations thereof. According to some embodiments, the salt comprises ammonium nitrate. According to some embodiments, the salt comprises ammonium sulfate. According to some embodiments, the salt comprises magnesium chloride. According to some embodiments, the salt comprises magnesium nitrate. According to some embodiments, the salt comprises lithium chloride. According to some embodiments, the salt comprises potassium sulfate. According to some embodiments, the salt comprises potassium nitrate. According to some embodiments, the salt comprises potassium chloride. According to some embodiments, the salt comprises potassium acetate. According to some embodiments, the salt comprises potassium hydroxide. According to some embodiments, the salt comprises sodium chloride. According to some embodiments, the salt comprises sodium nitrite. According to some embodiments, the salt comprises sodium dichromate. According to some embodiments, step (a) further comprises heating the aqueous salt solution to a predetermined temperature.

[0174] According to some embodiments, the gas mixture provided in step (a) comprises steam and the inert gas. According to some embodiments, the steam is superheated steam. Specifically, the advantage of superheated steam is the absence of liquid water therein. According to some embodiments, the water source 102 is a steamgenerator. According to some embodiments, the water source 102 is a superheated steam generator.

[0175] According to some embodiments, the gas mixture is provided in step (a) at a temperature Ta. According to some embodiments, the temperature Tais in the range of 5°C to 600°C, including each value and sub-range within the specified range. According to some embodiments, the gas mixture is provided in step (a) at a temperature Ta. According to some embodiments, the temperature Tais in the range of 15°C to 550°C. According to some embodiments, the temperature Tais in the range of 20°C to 550°C. According to some embodiments, temperature Tais in the range of 15°C to 400°C. According to some embodiments, temperature Tais in the range of 15°C to 300°C. According to some embodiments, temperature Tais in the range of 15°C to200°C. According to some embodiments, temperature Tais in the range of 15°C to100°C. According to some embodiments, temperature Tais in the range of 15°C to50°C. According to some embodiments, temperature Tais in the range of 15°C to 40°C.According to some embodiments, temperature Tais in the range of 200°C to 600°C. According to some embodiments, temperature Tais about room temperature. According to some embodiments, temperature Tais room temperature.

[0176] The term “about” means ±15%, ±10%, or ±5% of a specified value. Each possibility represents a separate embodiment of the invention.

[0177] According to some embodiments, step (a) comprises providing an aqueous salt solution in the water source 102 and flowing an inert gas using the inert gas source 104 over or through the aqueous salt solution, thereby forming the gas mixture and the temperature Tais in the range of 15°C to 50°C. Specifically, temperatures around room temperatures may be suitable for the salt solution method, according to some embodiments.

[0178] According to some embodiments, the gas mixture provided in step (a) comprises superheated steam and the temperature Tais in the range of 150°C to 600°C. Specifically, superheated steam temperatures may be applied for the superheated steam method using superheated steam generator as the inert gas source 104.

[0179] According to some embodiments, temperature Tais approximately equal to temperature Taof step (b), which is discussed herein.

[0180] The term “approximately equal” refers to two values, which are equal of differ one from the other by 15%, ±10%, or ±5%. Each possibility represents a separate embodiment of the invention.

[0181] According to some embodiments, providing the gas mixture in step (a) further comprises switching the gas mixture inlet valve 110 to an open state.

[0182] According to some embodiments, during step (a) the gas mixture inlet valve 110 is in an open state. According to some embodiments, during step (a) the first gas inlet valve 112 is in an open state. According to some embodiments, during step (a) the second gas inlet valve 114 is in a closed state. According to some embodiments, during step (a) the first gas outlet valve 128 is in an open state. According to some embodiments, during step (a) the second gas outlet valve 130 is in a closed state. According to some embodiments, during step (a) the intermediate tube valve 134 is in a closed state. According to some embodiments, during step (a) the first vacuum valve 140 is in a closed state. According to some embodiments, during step (a) the second vacuum valve 142 is in a closed state.

[0183] Specific reference is now made to step (b) of the present process. According to some embodiments, the present process comprises step (b) of contacting the gas mixture provided in step (a) with an alkali metal.

[0184] According to some embodiments, the contacting of step (b) entails forming hydrogen. According to some embodiments, the contacting of step (b) entails forming an alkali metal hydroxide (MA0H). According to some embodiments, the contacting of step (b) entails forming hydrogen and an alkali metal hydroxide (MA0H). According to some embodiments, the contacting of step (b) entails forming hydrogen and a mixture of the alkali metal (MA) and alkali metal hydroxide (MA0H).

[0185] According to some embodiments, the alkali metal of step (b) is sodium, potassium, a mixture or an alloy thereof. According to some embodiments, the alkali metal of step (b) is sodium or potassium. According to some embodiments, the alkali metal of step (b) comprises sodium or potassium. According to some embodiments, the alkali metal of step (b) comprises sodium or an alloy thereof. According to some embodiments, the alkali metal of step (b) comprises sodium. According to some embodiments, the alkali metal of step (b) is sodium. According to some embodiments, the alkali metal of step (b) comprises potassium or an alloy thereof. According to someembodiments, the alkali metal of step (b) comprises potassium. According to some embodiments, the alkali metal of step (b) is potassium.

[0186] It is to be understood that when sodium is the alkali metal, according to some embodiments, then the product is sodium hydroxide according to the following reaction scheme:

[0187] 0.5 H2.

[0188] It is to be also understood that when potassium is the alkali metal, according to some embodiments, then the product is potassium hydroxide according to the following reaction scheme:

[0189] 0.5 H2.

[0190] According to some embodiments, step (b) comprises contacting the water within the gas mixture with the alkali metal, wherein the alkali metal is in a molar excess over the contacted water. According to some embodiments, step (b) comprises contacting the gas mixture with the alkali metal, wherein the alkali metal is in a molar excess over the water within the gas mixture.

[0191] Specifically, step (d) of the present process, which will be elaborated below, involves a reaction between the alkali metal and the alkali metal hydroxide formed in step (b), according to some embodiments. Thus, the alkali metal may be provided to step (b) in excess, so that the excess non reacted alkali metal may react in step (d)

[0192] According to some embodiments, the molar ratio between the alkali metal and the contacted water is in the range of 1.1:1 to 4:1, including each value and subrange within the specified range. According to some embodiments, the molar ratio between the alkali metal and the contacted water is in the range of 0.5:1 to 3:1. According to some embodiments, the molar ratio between the alkali metal and the contacted water is in the range of 0.5:1 to 2.5:1. According to some embodiments, the molar ratio between the alkali metal and the contacted water is in the range of 0.3:1 to 2.25:1. According to some embodiments, the molar ratio between the alkali metal and the contacted water is in the range of 1.1:1 to 4:1, including each value and sub-range within the specified range. According to some embodiments, the molar ratio between the alkali metal and the contacted water is in the range of 1.25:1 to 3:1. According to some embodiments, the molar ratio between the alkali metal and the contacted water isin the range of 1.5: 1 to 2.5: 1. According to some embodiments, the molar ratio between the alkali metal and the contacted water is in the range of 1.75:1 to 2.25:1. According to some embodiments, the molar ratio between the alkali metal and the contacted water is in the range of 1.9:1 to 2.1:1. According to some embodiments, the molar ratio between the alkali metal and the contacted water is about 2:1.

[0193] According to some embodiments, the molar ratio between the alkali metal and the contacted water vapor is in the range of 1.1:1 to 4:1, including each value and sub-range within the specified range. According to some embodiments, the molar ratio between the alkali metal and the contacted water vapor is in the range of 1.25:1 to 3:1. According to some embodiments, the molar ratio between the alkali metal and the contacted water vapor is in the range of 1.5:1 to 2.5:1. According to some embodiments, the molar ratio between the alkali metal and the contacted water vapor is in the range of 1.75:1 to 2.25:1. According to some embodiments, the molar ratio between the alkali metal and the contacted water vapor is in the range of 1.9: 1 to 2.1 : 1. According to some embodiments, the molar ratio between the alkali metal and the contacted water vapor is about 2:1.

[0194] According to some embodiments, the contacting of step (b) in conducted within the first reaction chamber 150.

[0195] According to some embodiments, step (b) comprises flowing the gas mixture into the first reaction chamber 150. According to some embodiments, step (b) comprises flowing the gas mixture through the first gas mixture inlet tube 106 into the first reaction chamber 150. According to some embodiments, step (b) comprises flowing the gas mixture through the first gas mixture inlet 152 into the first reaction chamber 150. According to some embodiments, step (b) comprises flowing the gas mixture from the water source and / or inert gas source through the first gas mixture inlet tube 106 into the first reaction chamber 150. According to some embodiments, step (b) comprises flowing the gas mixture from the water source and / or inert gas source through the first gas mixture inlet 152 into the first reaction chamber 150. According to some embodiments, step (b) comprises flowing the gas mixture from the water source and inert gas source through the first gas mixture inlet tube 106 into the first reaction chamber 150. According to some embodiments, step (b) comprises flowing the gas mixture from the water source and inert gas through the first gas mixture inlet 152 intothe first reaction chamber 150. According to some embodiments, step (b) further comprises switching the first gas inlet valve 112 to an open state.

[0196] According to some embodiments, the first reaction chamber 150 contains the alkali metal. According to some embodiments, the first reaction chamber 150 contains the alkali metal at the beginning of step (b).

[0197] According to some embodiments, step (b) comprises flowing the gas mixture into the first reaction chamber 150 at a flow rate and time period that results in a molar ratio between the alkali metal and the water reacting therewith to be in the molar ratio specified above. According to some embodiments, step (b) comprises flowing the gas mixture into the first reaction chamber 150 at a flow rate and time period that results in a molar ratio between the alkali metal and the water vapor reacting therewith to be in the molar ratio specified above. According to some embodiments, step (b) comprises flowing the gas mixture through the first gas mixture inlet 152 into the first reaction chamber 150 at a flow rate and time period that results in a molar ratio between the alkali metal and the water reacting therewith to be in the molar ratio specified above. According to some embodiments, step (b) comprises flowing the gas mixture through the first gas mixture inlet 152 into the first reaction chamber 150 at a flow rate and time period that results in a molar ratio between the alkali metal and the water vapor reacting therewith to be in the molar ratio specified above. According to some embodiments, step (b) comprises flowing the gas mixture through the first gas mixture inlet tube 106 into the first reaction chamber 150 at a flow rate and time period that results in a molar ratio between the alkali metal and the water reacting therewith to be in the molar ratio specified above. According to some embodiments, step (b) comprises flowing the gas mixture through the first gas mixture inlet tube 106 into the first reaction chamber 150 at a flow rate and time period that results in a molar ratio between the alkali metal and the water vapor reacting therewith to be in the molar ratio specified above.

[0198] According to some embodiments, flowing the gas mixture into the first reaction chamber 150 results in the following chemical reaction:

[0199] 0.5 H2.

[0200] According to some embodiments, flowing the gas mixture into the first reaction chamber 150 results in the following chemical reaction:

[0201] MA+ H2O (g) -> MAOH + 0.5 H2(g).

[0202] According to some embodiments, flowing the gas mixture into the first reaction chamber 150 results in the following chemical reaction:

[0203] 0.5 H2(g).

[0204] According to some embodiments, flowing the gas mixture into the first reaction chamber 150 results in forming the hydrogen. According to some embodiments, flowing the gas mixture into the first reaction chamber 150 results in forming the hydrogen and the alkali metal hydroxide. According to some embodiments, flowing the gas mixture into the first reaction chamber 150 results in forming the hydrogen and the mixture of the excess alkali metal and alkali metal hydroxide.

[0205] According to some embodiments, step (b) further comprises monitoring the transformation of the alkali metal into the alkali metal hydroxide. According to some embodiments, the monitoring is carried out using the first detector 120. According to some embodiments, step (b) further comprises stopping the flow of the gas mixture into the first reaction chamber 150 when the molar ratio as specified herein is reached.

[0206] According to some embodiments, the first detector 120 is in functional communication with the first gas inlet valve 112, so that upon detection a predetermined conversion of alkali metal to alkali metal hydroxide, the first gas inlet valve 112 is automatically switched to a closed state.

[0207] It is to be understood that the predetermined conversion is equivalent to the molar ratio specified herein. For example, if the required molar ratio between contacted water and the alkali metal is 1:2, then the predetermined conversion of the alkali metal is 50%.

[0208] According to some embodiments, step (b) comprises flowing the gas mixture through the first gas inlet 152 into the first reaction chamber 150 to contact the alkali metal, induce the reaction and form the hydrogen and the mixture of the excess alkali metal and alkali metal hydroxide. According to some embodiments, step (b) further comprises flowing the formed hydrogen, the inert gas and optionally water vapor through the first gas outlet 154. According to some embodiments, flowing gas through the first gas outlet 154 maintains a predetermined pressure Pbwithin the first reaction chamber 150.

[0209] According to some embodiments, step (b) is performed at atmospheric pressure. Specifically, according to some embodiments, during step (b) both the first gas mixture inlet 152 and first gas outlet 154 are open, so that the gas pressure within the first reaction chamber 150, Pb, is maintained substantially equal to the ambient pressure. More specifically, according to some embodiments, during step (b) the gas mixture is flowing through the first gas mixture inlet 152 into the first reaction chamber 150, where at least some of the water vapor content is consumed and hydrogen gas forms. According to some embodiments, the gas composition within the first reaction chamber 150 is then comprising the inert gas, hydrogen and, optionally, unreacted water vapor. Then, according to some embodiments, when further gas mixture is flowing through the first gas mixture inlet 152 into the first reaction chamber 150, some of the gas composition is exiting through the first gas outlet 154 and out of the first reaction chamber 150. This sequence, according to some embodiments, results in maintenance of pressure, Pb, as substantially equal to the ambient pressure.

[0210] According to some embodiments, step (b) is performed at a pressure Pbof about 1 Bar. According to some embodiments, Pbis in the range of 0.7 Bar to 1.5 Bar. According to some embodiments, Pbis in the range of 0.75 Bar to 1.3 Bar. According to some embodiments, Pbis in the range of 0.8 Bar to 1.25 Bar. According to some embodiments, Pbis in the range of 0.85 Bar to 1.2 Bar. According to some embodiments, Pbis in the range of 0.9 Bar to 1.1 Bar. According to some embodiments, Pbis in the range of 0.95 Bar to 1.05 Bar.

[0211] According to some embodiments, step (b) is performed at a temperature Tbin the range of 5°C to 600°C, including each value and sub-range within the specified range. According to some embodiments, Tbis in the range of 10°C to 550°C. According to some embodiments, Tbis in the range of 15°C to 500°C. According to some embodiments, Tbis in the range of 15°C to 400°C. According to some embodiments, Tbis in the range of 15°C to 300°C. According to some embodiments, Tbis in the range of 15°C to 250°C. According to some embodiments, Tbis in the range of 15°C to 200°C. According to some embodiments, Tbis in the range of 15°C to 150°C. According to some embodiments, Tbis in the range of 15°C to 100°C. According to some embodiments, Tbis in the range of 15°C to 50°C. According to some embodiments, Tbis in the range of 15°C to 40°C. According to some embodiments, Tbis in the range of 5°C to 40°C.

[0212] According to some embodiments, step (b) is performed at a temperature Tbin the range of 5°C to 600°C. According to some embodiments, Tbis about room temperature. According to some embodiments, Tbis about 25°C.

[0213] According to some embodiments, Tbis substantially equal to Ta. According to some embodiments, steps (a) and (b) are performed at least partially simultaneously. According to some embodiments, steps (a) and (b) are performed simultaneously and Tbis substantially equal to Ta.

[0214] It is contemplated that a temperature gradient will be applied during step (b). Therefore, phrases, such as “step (b) is performed at a temperature Tbin the range of 5 °C to 600°C” are intended to cover temperature gradient that are included within or partially overlap with the 5°C to 600°C range.

[0215] According to some embodiments, step (b) comprises applying heat to the alkali metal. According to some embodiments, step (b) comprises applying heat to the first reaction chamber 150 by the first heater 116. According to some embodiments, applying heat comprises application of induction heating.

[0216] According to some embodiments, during step (b) the gas mixture inlet valve 110 is in an open state. According to some embodiments, during step (b) the first gas inlet valve 112 is in an open state. According to some embodiments, during step (b) the second gas inlet valve 114 is in a closed state. According to some embodiments, during step (b) the first gas outlet valve 128 is in an open state. According to some embodiments, during step (b) the second gas outlet valve 130 is in a closed state. According to some embodiments, during step (b) the intermediate tube valve 134 is in a closed state. According to some embodiments, during step (b) the first vacuum valve 140 is in a closed state. According to some embodiments, during step (b) the second vacuum valve 142 is in a closed state.

[0217] Specific embodiments of steps (a) and (b) are shown in Figure 3 (identifier 1) and Figure 4A. Specifically, Figure 3 and Figure 4A relate to particular embodiments, wherein the alkali metal is sodium.

[0218] Specific reference is now made to step (c) of the present process. According to some embodiments, step (c) is optional. According to some embodiments, the present process optionally comprises step (c) of isolating the hydrogen produced in step (b) from the mixture of the alkali metal and alkali metal hydroxide. According to someembodiments, the present process optionally comprises step (c) of separating the hydrogen produced in step (b) from the mixture of the alkali metal and alkali metal hydroxide.

[0219] As detailed herein step (c) is optional. Specifically. In both steps (b) and (d) of the present process, hydrogen gas is produced, according to some embodiments. According to some embodiments, the hydrogen formed in step (b) may be isolated from the reaction mixture (i) during step (c); (ii) during step (e) together with the hydrogen produced in step (d); or (iii) partially during step (c) and partially during step (e). Each possibility represents a separate embodiment of the invention.

[0220] According to some embodiments, the present process comprises performing step (c).

[0221] The term "isolating" as used herein, means separating a compound (e.g., hydrogen), alone or together with another compound (e.g., an inert gas) from another constituent of the process (e.g., an alkali metal, its hydroxide and / or oxide). The isolation generally results is a composition enriched with the separated compound, however the term is not limited to such enrichment. For example, in step (c), the hydrogen may be initially isolated, together with the inert gas and optionally water vapor, from the mixture of the alkali metal (MA) and alkali metal hydroxide (MA0H). In such example, the isolated gas mixture will be depleted from MAand MA0H, but it does not necessarily mean that it is enriched with hydrogen, since isolation requirements may require additional inert gas carrier within the isolated gas mixture, according to some embodiments. Similarly, with respect to the isolation of step (g), for example, the recycled alkali metal may be initially isolated, together with an inert gas and oxygen, from the reaction mixture within the first reaction chamber 150. Thus, according to some embodiments, isolating may include purification, but it is not limited to purification.

[0222] According to some embodiments, step (c) comprises flowing the formed hydrogen, the inert gas and optionally water vapor through the first gas outlet 154. According to some embodiments, flowing gas through the first gas outlet 154 maintains a predetermined pressure Pcwithin the first reaction chamber 150.

[0223] According to some embodiments, step (c) is performed at atmospheric pressure. Specifically, according to some embodiments, during step (c) both the firstgas mixture inlet 152 and first gas outlet 154 are open, so that the gas pressure within the first reaction chamber 150, Pc, is maintained substantially equal to the ambient pressure. More specifically, according to some embodiments, during step (b) the gas mixture is flowing through the first gas mixture inlet 152 into the first reaction chamber 150, where at least some of the water vapor content is consumed and hydrogen gas forms. According to some embodiments, the gas composition within the first reaction chamber 150 is then comprising the inert gas, hydrogen and, optionally, unreacted water vapor. Then, according to some embodiments, when further gas mixture is flowing through the first gas mixture inlet 152 into the first reaction chamber 150, some of the gas composition is exiting through the first gas outlet 154 and out of the first reaction chamber 150 in step (c). This sequence, according to some embodiments, results in maintenance of pressure, Pc, as substantially equal to the ambient pressure.

[0224] According to some embodiments, step (c) is performed at a pressure Pcof about 1 Bar. According to some embodiments, Pcis in the range of 0.7 Bar to 1.5 Bar. According to some embodiments, Pcis in the range of 0.75 Bar to 1.3 Bar. According to some embodiments, Pcis in the range of 0.8 Bar to 1.25 Bar. According to some embodiments, Pcis in the range of 0.85 Bar to 1.2 Bar. According to some embodiments, Pcis in the range of 0.9 Bar to 1.1 Bar. According to some embodiments, Pcis in the range of 0.95 Bar to 1.05 Bar.

[0225] According to some embodiments, step (c) is performed at a temperature Tcin the range of 5°C to 600°C, including each value and sub-range within the specified range.

[0226] According to some embodiments, Tcis substantially equal to Tb. According to some embodiments, steps (b) and (c) are performed at least partially simultaneously. According to some embodiments, steps (b) and (c) are performed simultaneously and Tbis substantially equal to Tc.

[0227] According to some embodiments, Ta, Tband Tcare substantially equal. According to some embodiments, steps (a), (b) and (c) are performed at least partially simultaneously. According to some embodiments, steps (a), (b) and (c) are performed simultaneously and Ta, Tband Tcare substantially equal.

[0228] According to some embodiments, step (c) comprises evacuating at least some of the hydrogen by vacuum. According to some embodiments, step (c) comprisesflowing the mixture of hydrogen, inert gas and optionally water vapor at about 1 Bar through the first gas outlet 154, and then evacuating the remaining mixture of hydrogen, inert gas and optionally water vapor, by vacuum. Thus, according to some embodiments, step (c) further comprises connecting the first gas outlet 154 to a vacuum source and applying vacuum to the first reaction chamber 150.

[0229] According to some embodiments, step (c) does not involve application of vacuum.

[0230] According to some embodiments, step (c) further comprises collecting the mixture of hydrogen, inert gas and optionally water vapor. According to some embodiments, step (c) further comprises collecting the hydrogen formed in step (b).

[0231] According to some embodiments, step (c) comprises flowing the formed hydrogen, the inert gas and optionally water vapor through the first gas outlet 154, thereby isolating the hydrogen produced in step (b) from the mixture of the alkali metal and alkali metal hydroxide.

[0232] According to some embodiments, step (c) further comprises further isolating the hydrogen from the inert gas and optionally water vapor. According to some embodiments, step (c) further comprises further isolating the hydrogen from the inert gas and optionally water vapor flown through the first gas outlet 154. According to some embodiments, step (c) further comprises collecting the hydrogen isolated from the mixture of the hydrogen, the inert gas and optionally water vapor.

[0233] According to some embodiments, the further hydrogen isolation comprises condensing the inert gas and optionally water vapor and recovering the hydrogen gas. Separation of gas mixtures through condensation is known in the art, and is typically performed under elevated pressure, reduced temperature or both. According to some embodiments, the further hydrogen isolation is performed using the gas separation unit 148.

[0234] The further hydrogen isolation of step (c) is shown in particular in Figure 3 identifier 8 (SEPARATION), which relates to the separation of hydrogen from the inert gas and unreacted water vapor, according to some embodiments, wherein the inert gas is argon and alkali metal is sodium. According to some embodiments, the further isolated hydrogen is then collected (identifier 10) and the separated inert gas and water mixture may be reused for an additional cycle of step (a).

[0235] Thus, according to some embodiments, step (c) further comprises reusing the inert gas and water vapor isolated from the hydrogen, in a consecutive repeat of step(a).

[0236] According to some embodiments, step (c) further comprises analyzing the hydrogen using the hydrogen analyzer 149.

[0237] According to some embodiments, step (c) further comprises further purifying the hydrogen isolated from the inert gas and optionally water vapor. According to some embodiments, step (c) further comprises collecting the purified hydrogen.

[0238] According to some embodiments, step (c) comprises flowing the hydrogen formed in step (b), the inert gas and optionally water vapor through the first gas outlet 154, wherein the first gas outlet valve 128 is in an open state, thereby isolating the hydrogen produced in step (b) from the mixture of the alkali metal and alkali metal hydroxide, which remains within the first reaction chamber 150.

[0239] According to some embodiments, during step (c) the gas mixture inlet valve 110 is in an open state. According to some embodiments, during step (c) the first gas inlet valve 112 is in an open state. According to some embodiments, during step (c) the second gas inlet valve 114 is in a closed state. According to some embodiments, during step (c) the first gas outlet valve 128 is in an open state. According to some embodiments, during step (c) the second gas outlet valve 130 is in a closed state. According to some embodiments, during step (c) the intermediate tube valve 134 is in a closed state. According to some embodiments, during step (c) the first vacuum valve 140 is in a closed state. According to some embodiments, during step (c) the second vacuum valve 142 is in a closed state.

[0240] Specific embodiments of step (c) are shown in Figure 3 (identifier 5) and Figure 4A. Specifically, Figure 3 and Figure 4A relate to particular embodiments, wherein the alkali metal is sodium.

[0241] Specific reference is now made to step (d) of the present process. According to some embodiments, the present process comprises step (d) of adjusting the temperature of the mixture of step (b) to a temperature Td. According to some embodiments, the temperature Td, is in the range of 200°C to 450°C, including each value and sub-range within the specified range. According to some embodiments, thetemperature adjustment entails inducing a reaction between the alkali metal and alkali metal hydroxide. According to some embodiments, the reaction results in the formation of hydrogen. According to some embodiments, the reaction results in the formation of an alkali metal oxide (MA2O). According to some embodiments, the reaction results in the formation of hydrogen and an alkali metal oxide (MA2O).

[0242] According to some embodiments, the reaction of step (d) entails forming hydrogen. According to some embodiments, the reaction of step (d) entails forming an alkali metal oxide (MA2O). According to some embodiments, the reaction of step (d) entails forming hydrogen and an alkali metal oxide.

[0243] According to some embodiments, the reaction of step (d) substantially consumes the alkali metal of step (b). As used herein “substantially consumes” means that no more than 5%, 4%, 3%, 2% or 1% of the alkali metal remains. Each possibility represents a separate embodiment of the invention.

[0244] According to some embodiments, the alkali metal hydroxide of step (d) is sodium hydroxide, potassium hydroxide or a mixture thereof. According to some embodiments, the alkali metal hydroxide of step (d) is sodium hydroxide or potassium hydroxide. According to some embodiments, the alkali metal hydroxide of step (d) comprises sodium hydroxide or potassium hydroxide. According to some embodiments, the alkali metal hydroxide of step (d) comprises sodium hydroxide. According to some embodiments, the alkali metal hydroxide of step (d) is sodium hydroxide. According to some embodiments, the alkali metal of step (d) comprises potassium hydroxide. According to some embodiments, the alkali metal hydroxide of step (d) is potassium hydroxide.

[0245] It is to be understood that when sodium hydroxide is the alkali metal hydroxide, according to some embodiments, then the product is sodium oxide according to the following reaction scheme:

[0246] 0.5 H2.

[0247] It is to be also understood that when potassium hydroxide is the alkali metal hydroxide, according to some embodiments, then the product is potassium oxide according to the following reaction scheme:

[0248] 0.5 H2.

[0249] According to some embodiments, the reaction of step (d), according to some embodiments, is performed under separate conditions of those of step (b) and involves an additional reduction of the alkali metal hydroxide (MA0H) using the alkali metal (MA), as follows:

[0250] MA+ MA0H MA2O + 1 / 2H2.

[0251] According to some embodiments, at least one of the reaction temperature of step (d) and reaction pressure of step (d) is different than the reaction temperature of step (b) and reaction pressure is of step (b). Each possibility represents a separate embodiment of the invention.

[0252] According to some embodiments, step (d) is performed substantially in the absence of water. Specifically, during steps (b) and (c) substantially all the water vapor is either consumed or evacuated through the first gas outlet 154.

[0253] According to some embodiments, step (d) is performed under inert gas. According to some embodiments, the inert gas is the inert gas of step (a). According to some embodiments, the inert gas is the same compound as the inert gas of step (a).

[0254] According to some embodiments, the contacting of step (d) in conducted within the first reaction chamber 150.

[0255] According to some embodiments, step (d) is performed at a pressure Pdin the range of 0.9 Bar to 2 Bar, including each value and sub-range within the specified range. According to some embodiments, step (d) is performed at atmospheric pressure. According to some embodiments, step (d) is performed at a pressure Pdof about 1 Bar. According to some embodiments, Pdis in the range of 0.7 Bar to 1.5 Bar. According to some embodiments, Pdis in the range of 0.75 Bar to 1.3 Bar. According to some embodiments, Pdis in the range of 0.8 Bar to 1.25 Bar. According to some embodiments, Pdis in the range of 0.85 Bar to 1.2 Bar. According to some embodiments, Pdis in the range of 0.9 Bar to 1.1 Bar. According to some embodiments, Pdis in the range of 0.95 Bar to 1.05 Bar. According to some embodiments, the pressure Pdis substantially equal to the pressure Pb.

[0256] Specifically, according to some embodiments, step (d) may be conducted wherein the first gas outlet valve 128 is in a closed state or in an open state, wherein in the open state of the first gas outlet valve 128 gas is allowed to exit the first reactionchamber 150 through the first gas outlet 154, and wherein in the closed state of the first gas outlet valve 128 gas is not allowed to exit the first reaction chamber 150 through the first gas outlet 154. Thus, according to embodiments wherein the gas outlet valve 128 is in an open state, the pressure Pdis maintained substantially at ambient pressure, whereas according to embodiments wherein the gas outlet valve 128 is in a closed state, the pressure Pdis may elevate above ambient pressure.

[0257] It is to be understood that anyone of valves 110, 112, 114, 128, 130, 140 and 142 may, individually, be a unidirectional valve, which in its open states allows flow therethrough according to the flow direction described herein (i.e., valves 110 and 112 into the first reaction chamber 150; valves 114 and 112 into the second reaction chamber 170; valves 128 and 140 out of the first reaction chamber 150; and valves 130 and 142 out of the second reaction chamber 170), while preventing flow in the opposite direction, according to some embodiments. Each possibility represents a separate embodiment of the invention.

[0258] According to some embodiments, Tdis in the range of 100°C to 600°C, including each value and sub-range within the specified range. According to some embodiments, Tdis in the range of 200°C to 500°C, including each value and sub-range within the specified range. According to some embodiments, Tdis in the range of 220°C to 450°C. According to some embodiments, Tdis in the range of 250°C to 400°C. According to some embodiments, Tdis in the range of 275°C to 400°C. According to some embodiments, Tdis in the range of 300°C to 400°C. According to some embodiments, Tdis in the range of 325°C to 375°C. According to some embodiments, Tdis about 350°C.

[0259] According to some embodiments, Tdis at least 50°C higher than Tb. According to some embodiments, Tdis at least 100°C higher than Tb. According to some embodiments, Tdis at least 150°C higher than Tb. According to some embodiments, Tdis at least 200°C higher than Tb. According to some embodiments, Tdis at least 250°C higher than Tb. According to some embodiments, Tdis at least 300°C higher than Tb.

[0260] It is contemplated that a temperature gradient will be applied during step (d). Therefore, phrases, such as “Tdis in the range of 200°C to 500°C” are intended tocover temperature gradient that are included within or partially overlap with the 200°C to 500°C range.

[0261] According to some embodiments, step (d) comprises applying heat to the alkali metal and the alkali metal hydroxide. According to some embodiments, step (d) comprises applying heat to the first reaction chamber 150 by the first heater 116. According to some embodiments, applying heat comprises application of induction heating.

[0262] According to some embodiments, step (d) comprises switching the first gas inlet valve 110 to a closed state; and adjusting the temperature of the first reaction chamber 150 to the temperature Tdusing the first heater 116, thereby forming hydrogen and the alkali metal oxide.

[0263] According to some embodiments, during step (d) the gas mixture inlet valve 110 is in a closed state. According to some embodiments, during step (d) the first gas inlet valve 112 is in a closed state. According to some embodiments, during step (d) the second gas inlet valve 114 is in a closed state. According to some embodiments, during step (d) the first gas outlet valve 128 is in an open state. According to some embodiments, during step (d) the first gas outlet valve 128 is in a closed state. According to some embodiments, during step (d) the second gas outlet valve 130 is in a closed state. According to some embodiments, during step (d) the intermediate tube valve 134 is in a closed state. According to some embodiments, during step (d) the first vacuum valve 140 is in a closed state. According to some embodiments, during step (d) the second vacuum valve 142 is in a closed state.

[0264] Specific embodiments of step (d) are shown in Figure 3 (identifier 2) and Figure 4B. Specifically, Figure 3 and Figure 4B relate to particular embodiments, wherein the alkali metal is sodium and.

[0265] Specific reference is now made to step (e) of the present process. According to some embodiments, the present process comprises step (e) of isolating the hydrogen produced in step (d). According to some embodiments, step (e) comprises optionally isolating the hydrogen produced in step (d) from the alkali metal oxide. According to some embodiments, step (e) further comprises optionally isolating the hydrogen produced in step (b) from the alkali metal oxide.

[0266] It is to be understood that the hydrogen formed in step (b) may be isolated in step (c), and / or, later together with the hydrogen formed in step (d) during in step (e). Each possibility represents a separate embodiment of the invention. It is contemplated that some of the hydrogen formed in step (b) is isolated in step (c), and the remainder of which is isolated during in step (e).

[0267] The term "isolating" is as defined hereinabove. For example, in step (e), the hydrogen may be isolated, together with the inert gas and, optionally, trace water vapor, from the reaction mixture comprising the alkali metal oxide (MA2O). In such example, the isolated gas mixture will be depleted from MA2O, but it does not necessarily mean that it is enriched with hydrogen, since isolation requirements may require additional inert gas carrier within the isolated gas mixture, according to some embodiments. Thus, according to some embodiments, isolating may include purification, but it is not limited to purification.

[0268] According to some embodiments, step (e) comprises flowing the formed hydrogen, the inert gas and optionally water vapor through the first gas outlet 154. According to some embodiments, flowing gas through the first gas outlet 154 results in a predetermined pressure Pewithin the first reaction chamber 150.

[0269] According to some embodiments, step (e) is performed at atmospheric pressure. According to some embodiments, step (e) results in an atmospheric pressure within the first reaction chamber 150. Specifically, according to some embodiments, during step (d) the first gas outlet 154 are open, so that the gas pressure within the first reaction chamber 150, Pd, is maintained substantially equal to the ambient pressure. More specifically, according to some embodiments, during step (d) hydrogen is formed within the first reaction chamber 150. According to some embodiments, the gas composition with the first reaction chamber 150 is then comprising the inert gas, hydrogen and, optionally, trace unreacted water vapor. Then, according to some embodiments, when hydrogen forms within the first reaction chamber 150, some of the gas composition is exiting through the first gas outlet 154 and out of the first reaction chamber 150 in step (e). This sequence, according to some embodiments, results in maintenance of pressure, Peat the end of step (e), as substantially equal to the ambient pressure.

[0270] According to some embodiments, pressure Peat the end of step (e)is about 1 Bar. According to some embodiments, Peis in the range of 0.7 Bar to 1.5 Bar. According to some embodiments, Peis in the range of 0.75 Bar to 1.3 Bar. According to some embodiments, Peis in the range of 0.8 Bar to 1.25 Bar. According to some embodiments, Peis in the range of 0.85 Bar to 1.2 Bar. According to some embodiments, Peis in the range of 0.9 Bar to 1.1 Bar. According to some embodiments, Peis in the range of 0.95 Bar to 1.05 Bar.

[0271] According to some embodiments, Peis substantially equal to Pd. According to some embodiments, steps (d) and (e) are performed at least partially simultaneously. According to some embodiments, steps (d) and (e) are performed simultaneously and Pdis substantially equal to Pe.

[0272] According to some embodiments, Pa, Pb, Pc, Pdand Peare substantially equal.

[0273] According to some embodiments, step (e) is performed at a temperature Tcin the range of 200°C to 500°C, including each value and sub-range within the specified range.

[0274] According to some embodiments, Tdis substantially equal to Te. According to some embodiments, steps (d) and (e) are performed at least partially simultaneously. According to some embodiments, steps (d) and (e) are performed simultaneously and Tdis substantially equal to Te.

[0275] According to some embodiments, Ta, Tb, Tc, Tdand Teare substantially equal.

[0276] According to some embodiments, step (e) comprises evacuating at least some of the hydrogen by vacuum. According to some embodiments, step (e) comprises flowing the mixture of hydrogen, inert gas and optionally trace water vapor at about 1 Bar through the first gas outlet 154, and then evacuating the remaining mixture of hydrogen, inert gas and optionally trace water vapor, by vacuum. Thus, according to some embodiments, step (e) further comprises connecting the first gas outlet 154 to a vacuum source and applying vacuum to the first reaction chamber 150.

[0277] According to some embodiments, step (e) does not involve application of vacuum.

[0278] According to some embodiments, step (e) further comprises collecting the mixture of hydrogen, inert gas and optionally water vapor. According to some embodiments, step (e) further comprises collecting the hydrogen formed in step (d). According to some embodiments, step (e) further comprises collecting the hydrogen formed in step (b).

[0279] According to some embodiments, step (e) comprises flowing the formed hydrogen, the inert gas and optionally trace water vapor through the first gas outlet 154, thereby isolating the hydrogen produced in step (d) from the alkali metal oxide. According to some embodiments, step (e) comprises flowing the formed hydrogen, the inert gas and optionally trace water vapor through the first gas outlet 154, thereby isolating the hydrogen produced in step (d) and the hydrogen produced in step (b) from the alkali metal oxide.

[0280] According to some embodiments, step (e) further comprises further isolating the hydrogen from the inert gas and optionally water vapor. According to some embodiments, step (e) further comprises further isolating the hydrogen from the inert gas and optionally water vapor flown through the first gas outlet 154. According to some embodiments, step (e) further comprises collecting the hydrogen isolated from the mixture of the hydrogen, the inert gas and optionally water vapor.

[0281] According to some embodiments, the further hydrogen isolation comprises condensing the inert gas and optionally water vapor and recovering the hydrogen gas. Separation of gas mixtures through condensation is known in the art, and is typically performed under elevated pressure, reduced temperature or both. According to some embodiments, the further hydrogen isolation is performed using the gas separation unit 148.

[0282] The further hydrogen isolation of step (e) is shown in particular in Figure 3 identifier 8 (SEPARATION), which relates to the separation of hydrogen from the inert gas and unreacted water vapor, according to some embodiments, wherein the inert gas is argon and alkali metal is sodium. According to some embodiments, the further isolated hydrogen is then collected (identifier 10) and the separated inert gas and water mixture may be reused for an additional cycle of step (a).

[0283] Thus, according to some embodiments, step (e) further comprises reusing the inert gas and water vapor isolated from the hydrogen, in a consecutive repeat of step(a).

[0284] According to some embodiments, step (e) further comprises analyzing the hydrogen using the hydrogen analyzer 149.

[0285] According to some embodiments, step (e) further comprises further purifying the hydrogen isolated from the inert gas and optionally water vapor. According to some embodiments, step (e) further comprises collecting the purified hydrogen.

[0286] According to some embodiments, step (e) comprises flowing the hydrogen, the inert gas and optionally water vapor through the first gas outlet 154, wherein the first gas outlet valve 128 is in an open state, thereby isolating the hydrogen from the alkali metal oxide, which remains within the first reaction chamber 150.

[0287] According to some embodiments, during step (e) the gas mixture inlet valve 110 is in a closed state. According to some embodiments, during step (e) the first gas inlet valve 112 is in a closed state. According to some embodiments, during step (e) the second gas inlet valve 114 is in a closed state. According to some embodiments, during step (e) the first gas outlet valve 128 is in an open state. According to some embodiments, during step (e) the second gas outlet valve 130 is in a closed state. According to some embodiments, during step (e) the intermediate tube valve 134 is in a closed state. According to some embodiments, during step (e) the first vacuum valve 140 is in a closed state. According to some embodiments, during step (e) the second vacuum valve 142 is in a closed state.

[0288] Specific embodiments of step (e) are shown in Figure 3 (identifier 6) and Figure 4B. Specifically, Figure 3 and Figure 4B relate to particular embodiments, wherein the alkali metal is sodium.

[0289] Specific reference is now made to step (f) of the present process. According to some embodiments, the present process comprises step (f) of adjusting the alkali metal oxide formed in step (e) to a temperature Tf. According to some embodiments, temperature Tfis in the range of 400°C to 1000°C, including each value and sub-range within the specified range. According to some embodiments, step (f) comprises adjusting the alkali metal oxide formed in step (e) to a pressure Pf. According to someembodiments, the pressure Pfis in the range of 0.1 torr to 100 torr. According to some embodiments, the temperature and / or pressure adjustment of step (f) entails inducing a decomposition of the alkali metal oxide. According to some embodiments, the decomposition of the alkali metal oxide results in a recycled alkali metal and oxygen.

[0290] According to some embodiments, the reaction of step (f) entails forming oxygen. According to some embodiments, the reaction of step (f) entails forming a recycled alkali metal (MA). According to some embodiments, the reaction of step (f) entails forming oxygen and a recycled alkali metal.

[0291] According to some embodiments, the reaction of step (f) substantially consumes the alkali metal oxide of step (e). As used herein “substantially consumes” means that no more than 5%, 4%, 3%, 2% or 1% of the alkali metal oxide remains. Each possibility represents a separate embodiment of the invention.

[0292] According to some embodiments, the recycled alkali metal of step (f) is sodium, potassium, a mixture or an alloy thereof. According to some embodiments, the recycled alkali metal of step (f) is sodium or potassium. According to some embodiments, the recycled alkali metal of step (f) comprises sodium or potassium. According to some embodiments, the recycled alkali metal of step (f) comprises sodium or an alloy thereof. According to some embodiments, the recycled alkali metal of step (f) comprises sodium. According to some embodiments, the recycled alkali metal of step (f) is sodium. According to some embodiments, the recycled alkali metal of step (f) comprises potassium or an alloy thereof. According to some embodiments, the recycled alkali metal of step (f) comprises potassium. According to some embodiments, the recycled alkali metal of step (f) is potassium.

[0293] It is to be understood that when sodium oxide is the alkali metal oxide, according to some embodiments, then the product is sodium according to the following reaction scheme:

[0294] 0.5 O2.

[0295] It is to be understood that when potassium oxide is the alkali metal oxide, according to some embodiments, then the product is potassium according to the following reaction scheme:

[0296] 0.5 O2.

[0297] Lastly, according to some embodiments, the reaction of step (f), according to some embodiments, is performed under separate conditions of those of steps (b) and (d) and involves a thermal decomposition under vacuum of the alkali metal oxide (MA2O) to recycle the alkali metal, as follows:

[0299] According to some embodiments, at least one of the reaction temperature of step (f) and reaction pressure of step (f) is different than the reaction temperature of step (b) and reaction pressure is of step (b). Each possibility represents a separate embodiment of the invention. According to some embodiments, at least one of the reaction temperature of step (f) and reaction pressure of step (f) is different than the reaction temperature of step (d) and reaction pressure is of step (d). Each possibility represents a separate embodiment of the invention.

[0300] According to some embodiments, step (f) is performed substantially in the absence of water. According to some embodiments, step (f) is performed substantially in the absence of hydrogen. According to some embodiments, step (f) is performed substantially in the absence of water and hydrogen. Specifically, during steps (b) and (c) substantially all the water vapor is either consumed or evacuated through the first gas outlet 154 and trace residual water vapor are further substantially evacuated during step (e). Hydrogen, according to some embodiments, is substantially evacuated during step (e) and, optionally, step (c).

[0301] According to some embodiments, the contacting of step (f) in conducted within the first reaction chamber 150.

[0302] According to some embodiments, step (f) is performed under vacuum. Specifically, it was found the vacuum accelerates the decomposition of MA2O and is suitable for the present reaction sequence and system 100.

[0303] According to some embodiments, step (f) is performed at a pressure Pfin the range of 0.1 Torr to 600 Torr, including each value and sub-range within the specified range. According to some embodiments, step (f) is performed at sub- atmospheric pressure. According to some embodiments, step (f) is performed at a pressure Pfof about 1 Torr. According to some embodiments, Pfis in the range of 0.1 Torr to 500 Torr. According to some embodiments, Pfis in the range of 0.1 Torr to 400 Torr. According to some embodiments, Pfis in the range of 0.1 Torr to 300 Torr.According to some embodiments, Pfis in the range of 0.1 Torr to 200 Torr. According to some embodiments, Pfis in the range of 0.1 Torr to 150 Torr. According to some embodiments, Pfis in the range of 0.1 Torr to 100 Torr. According to some embodiments, Pfis in the range of 0.1 Torr to 50 Torr. According to some embodiments, Pfis in the range of 0.1 Torr to 25 Torr. According to some embodiments, Pfis in the range of 0.1 Torr to 10 Torr. According to some embodiments, Pfis in the range of 0.2 Torr to 8 Torr. According to some embodiments, Pfis in the range of 0.3 Torr to 5 Torr. According to some embodiments, Pfis in the range of 0.5 Torr to 2 Torr. According to some embodiments, Pfis about 1 Torr. According to some embodiments, the pressure Peis lower than the pressure Pb.

[0304] According to some embodiments, step (f) comprises switching the first gas inlet valve 112 to a closed state. According to some embodiments, step (f) comprises switching the second gas inlet valve 114 to a closed state. According to some embodiments, step (f) comprises switching the first gas outlet valve 128 to a closed state.

[0305] It is to be understood that the phrase “switching a valve to an open state” as used herein entail either switching the particular valve from a closed to an open state or maintaining the valve in an open state. Similarly, the phrase “switching a valve to a closed state” as used herein entail either switching the particular valve from an open to a closed state or maintaining the valve in a closed state.

[0306] According to some embodiments, step (f) comprises switching the intermediate tube valve 134 to an open state to form fluid communication between the first reaction chamber 150 and the second reaction chamber 170. According to some embodiments, step (f) comprises switching the second vacuum valve 142 to an open state.

[0307] According to some embodiments, step (f) comprises applying vacuum using the second vacuum source 146. According to some embodiments, step (f) comprises applying vacuum to the first reaction chamber 150 using the second vacuum source 146. According to some embodiments, step (f) comprises applying vacuum to the second reaction chamber 170 using the second vacuum source 146. According to some embodiments, step (f) comprises applying vacuum to each one of the first reaction chamber 150 and second reaction chamber 170 using the second vacuum source 146.

[0308] Specifically, according to some embodiments, in step (f) vacuum is applied using the second vacuum source 146. According to some embodiments, the applied vacuum creates suction through the second vacuum tube 138. According to some embodiments, the applied vacuum creates suction through the second vacuum opening 178. According to some embodiments, the vacuum applied to the second vacuum opening 178 creates vacuum within the second reaction chamber 170. According to some embodiments, the applied vacuum creates suction through the second intermediate opening 176. According to some embodiments, the applied vacuum creates suction through the intermediate tube 132. According to some embodiments, the applied vacuum creates suction through the first intermediate opening 156. According to some embodiments, the vacuum applied to the first intermediate opening 156 creates vacuum within the first reaction chamber 150.

[0309] According to some embodiments, upon the application of vacuum, the pressure within the second reaction chamber 170 is Pf. According to some embodiments, upon the application of vacuum, the pressure within the first reaction chamber 150 is Pf. Pressure Pfis detailed in embodiments above,

[0310] According to some embodiments, step (f) comprising adjusting the first reaction chamber 150 to temperature Tfto induce the decomposition of the alkali metal oxide.

[0311] According to some embodiments, Tfis in the range of 200°C to 1000°C, including each value and sub-range within the specified range. According to some embodiments, Tfis in the range of 300°C to 800°C. According to some embodiments, Tfis in the range of 400°C to 700°C. According to some embodiments, Tfis in the range of 450°C to 650°C. According to some embodiments, Tfis in the range of 500°C to 600°C. According to some embodiments, Tfis in the range of 525°C to 575°C. According to some embodiments, Tfis about 550°C.

[0312] According to some embodiments, Tfis at least 100°C higher than Tb. According to some embodiments, Tfis at least 200°C higher than Tb. According to some embodiments, Tfis at least 150°C higher than Tb. According to some embodiments, Tfis at least 300°C higher than Tb. According to some embodiments, Tfis at least 400°C higher than Tb. According to some embodiments, Tfis at least 500°C higher than Tb.

[0313] According to some embodiments, Tfis higher than Td. According to some embodiments, Tfis at least 50°C higher than Td. According to some embodiments, Tfis at least 100°C higher than Td. According to some embodiments, Tfis at least 150°C higher than Td.

[0314] It is contemplated that a temperature gradient will be applied during step (d). Therefore, phrases, such as “Tfis in the range of 200°C to 1000°C” are intended to cover temperature gradient that are included within or partially overlap with the 200°C to 1000°C range.

[0315] According to some embodiments, step (f) comprises applying heat to the alkali metal oxide. According to some embodiments, step (f) comprises applying heat to the first reaction chamber 150 by the first heater 116. According to some embodiments, applying heat comprises application of induction heating.

[0316] According to some embodiments, during step (f) the gas mixture inlet valve 110 is in a closed state. According to some embodiments, during step (f) the first gas inlet valve 112 is in a closed state. According to some embodiments, during step (f) the second gas inlet valve 114 is in a closed state. According to some embodiments, during step (f) the first gas outlet valve 128 is in a closed state. According to some embodiments, during step (f) the first gas outlet valve 128 is in a closed state. According to some embodiments, during step (f) the second gas outlet valve 130 is in a closed state. According to some embodiments, during step (f) the intermediate tube valve 134 is in an open state. According to some embodiments, during step (f) the first vacuum valve 140 is in a closed state. According to some embodiments, during step (f) the second vacuum valve 142 is in an open state.

[0317] Specific embodiments of step (f) are shown in Figure 3 (identifier 3) and Figure 4C. Specifically, Figure 3 and Figure 4C relate to particular embodiments, wherein the alkali metal is sodium.

[0318] Specific reference is now made to step (g) of the present process. According to some embodiments, the present process comprises step (g) of isolating the recycled alkali metal produced in step (f).

[0319] The term "isolating" is as defined hereinabove. In particular, according to some embodiments, isolating may include purification, but it is not limited to purification.

[0320] According to some embodiments, the recycled alkali metal is isolated in step (g) in a sufficient purity so as to allow subsequent reaction thereof with water vapor according to the conditions of step (a).

[0321] According to some embodiments, step (g) comprises isolating the recycled alkali metal produced in step (f) by vacuum distillation. It is to be understood that, according to some embodiments, the alkali metal is at least partially in gas state in step (g)-

[0322] According to some embodiments, step (g) comprises flowing the formed recycled alkali metal and oxygen through the first intermediate opening 156 by vacuum suction. According to some embodiments, step (g) comprises flowing the formed recycled alkali metal and oxygen through the first intermediate opening 156, the intermediate tube 132 and the second intermediate opening 176 by vacuum suction using the second vacuum source 146.

[0323] According to some embodiments, the application of vacuum 154 results in a predetermined pressure Pgwithin the first reaction chamber 150. According to some embodiments, the application of vacuum 154 results in a predetermined pressure Pgwithin the second reaction chamber 170. According to some embodiments, the application of vacuum 154 results in a predetermined pressure Pgwithin the first reaction chamber 150 and the second reaction chamber 170.

[0324] According to some embodiments, step (g) is performed at a pressure Pgin the range of 0.1 Torr to 100 Torr, including each value and sub-range within the specified range. According to some embodiments, step (g) is performed at sub- atmospheric pressure. According to some embodiments, step (g) is performed at a pressure Pgof about 1 Torr. According to some embodiments, Pgis in the range of 0.1 Torr to 50 Torr. According to some embodiments, Pgis in the range of 0.1 Torr to 25 Torr. According to some embodiments, Pgis in the range of 0.1 Torr to 10 Torr. According to some embodiments, Pgis in the range of 0.2 Torr to 8 Torr. According to some embodiments, Pgis in the range of 0.3 Torr to 5 Torr. According to some embodiments, Pgis in the range of 0.5 Torr to 2 Torr. According to some embodiments, Pgis about 1 Torr.

[0325] According to some embodiments, Pgis substantially equal to Pf. According to some embodiments, steps (g) and (f) are performed at least partially simultaneously.According to some embodiments, steps (f) and (g) are performed simultaneously and Pfis substantially equal to Pg.

[0326] According to some embodiments, the pressure Pgis lower than the pressure Pb.

[0327] According to some embodiments, step (g) comprises applying vacuum using the second vacuum source 146, so that the pressure within the first reaction chamber 150 and second reaction chamber 170 is Pg.

[0328] According to some embodiments, step (g) comprises adjusting the first reaction chamber 150 to temperature Tgl; adjusting the second reaction chamber to temperature Tg2, which is lower than Tgl; and applying vacuum, so that the pressure within the first reaction chamber 150 and second reaction chamber 170, Pg, is sub- atmospheric.

[0329] According to some embodiments, the alkali metal is in a condense phase at Tg2and Pg. According to some embodiments, the alkali metal is solid or liquid at Tg2and Pg. According to some embodiments, the alkali metal is solid at Tg2and Pg. According to some embodiments, the alkali metal is liquid at Tg2and Pg.

[0330] According to some embodiments, the alkali metal at least partially vaporizes at Tgland Pg. Specifically, while, according to some embodiments, it is not required that the major phase of the recycled alkali metal in step (g) is gas, it is required that it at least gradually gasified for its isolation, as described herein.

[0331] According to some embodiments, Tglis in the range of 200°C to 1000°C, including each value and sub-range within the specified range. According to some embodiments, Tglis in the range of 300°C to 800°C. According to some embodiments, Tfis in the range of 400°C to 700°C. According to some embodiments, Tglis in the range of 450°C to 650°C. According to some embodiments, Tglis in the range of 500°C to 600°C. According to some embodiments, Tglis in the range of 525°C to 575°C. According to some embodiments, Tglis about 550°C.

[0332] According to some embodiments, Tglis at least 100°C higher than Tb. According to some embodiments, Tglis at least 200°C higher than Tb. According to some embodiments, Tglis at least 150°C higher than Tb. According to some embodiments, Tglis at least 300°C higher than Tb. According to some embodiments,Tglis at least 400°C higher than Tb. According to some embodiments, Tglis at least 500°C higher than Tb.

[0333] According to some embodiments, Tglis higher than Td. According to some embodiments, Tglis at least 50°C higher than Td. According to some embodiments, Tglis at least 100°C higher than Td. According to some embodiments, Tglis at least 150°C higher than Td.

[0334] According to some embodiments, Tglis substantially equal to Tf. According to some embodiments, steps (f) and (g) are performed at least partially simultaneously. According to some embodiments, steps (f) and (g) are performed simultaneously and Tfis substantially equal to Tgl.

[0335] According to some embodiments, step (g) comprises applying heat to the recycled alkali metal. According to some embodiments, step (g) comprises applying heat to the first reaction chamber 150 by the first heater 116. According to some embodiments, applying heat comprises application of induction heating.

[0336] According to some embodiments, Tg2is in the range of -30°C to 300°C, including each value and sub-range within the specified range. According to some embodiments, Tg2is in the range of 0°C to 200°C. According to some embodiments, Tg2is in the range of 5°C to 100°C. According to some embodiments, Tg2is in the range of 10°C to 50°C. According to some embodiments, Tg2is in the range of 10°C to 40°C. According to some embodiments, Tg2is in the range of 15°C to 35°C. According to some embodiments, Tg2is about room temperature. According to some embodiments, Tg2is about 25°C.

[0337] According to some embodiments, Tg2is lower than Tgl. According to some embodiments, Tglis at least 50°C higher than Tg2. According to some embodiments, Tglis at least 100°C higher than Tg2. According to some embodiments, Tglis at least 150°C higher than Tg2. According to some embodiments, Tglis at least 200°C higher than Tg2. According to some embodiments, Tglis at least 250°C higher than Tg2. According to some embodiments, Tglis at least 300°C higher than Tg2. According to some embodiments, Tglis at least 350°C higher than Tg2. According to some embodiments, Tglis at least 400°C higher than Tg2. According to some embodiments, Tglis at least 450°C higher than Tg2. According to some embodiments, Tglis at least 500°C higher than Tg2.

[0338] According to some embodiments, step (g) comprises evaporating the recycled alkali metal in the first reaction chamber 150. According to some embodiments, step (g) comprises condensing the recycled alkali metal in the second reaction chamber 170.

[0339] According to some embodiments, step (g) does not comprises collecting the recycled alkali metal. According to some embodiments, step (g) does not comprise purifying collecting the recycled alkali metal.

[0340] According to some embodiments, during step (g) the gas mixture inlet valve 110 is in a closed state. According to some embodiments, during step (g) the first gas inlet valve 112 is in a closed state. According to some embodiments, during step (g) the second gas inlet valve 114 is in a closed state. According to some embodiments, during step (g) the first gas outlet valve 128 is in a closed state. According to some embodiments, during step (g) the first gas outlet valve 128 is in a closed state. According to some embodiments, during step (g) the second gas outlet valve 130 is in a closed state. According to some embodiments, during step (g) the intermediate tube valve 134 is in an open state. According to some embodiments, during step (g) the first vacuum valve 140 is in a closed state. According to some embodiments, during step (g) the second vacuum valve 142 is in an open state.

[0341] Specific embodiments of step (g) are shown in Figure 3 (identifiers 4 and 7) and Figure 4D. Specifically, Figure 3 and Figure 4D relate to particular embodiments, wherein the alkali metal is sodium.

[0342] Specific reference is now made to a step of reusing the recycled alkali metal isolated in step (f) of present process. According to some embodiments, the present process comprises repeating steps (a) to (g) at least once, by reusing the recycled alkali metal isolated in step (f) for subsequent use in repeated step (b).

[0343] According to some embodiments, the present process comprises repeating steps (a) to (g) a plurality of times, each cycle by reusing the recycled alkali metal isolated in each step (f) for subsequent use in each repeated step (b).

[0344] Specifically, as detailed herein in the initial steps (a) to (g), according to some embodiments, a gas mixture is provided through the first gas mixture inlet 152 to the first reaction chamber 150, where a reaction between the water vapor and the alkali metal takes place to form hydrogen and a mixture of the alkali metal and alkali metalhydroxide. Then, according to some embodiments, the hydrogen formed is optionally isolated by flowing out of the first reaction chamber 150 through the first gas outlet 154. Thereafter, according to some embodiments, the temperature within the first reaction chamber 150 is adjusted to temperature Td(e.g., using the first heater 116) to induce a reaction between the alkali metal and alkali metal hydroxide within the first reaction chamber 150, thereby forming hydrogen and an alkali metal oxide therein. Then, according to some embodiments, the hydrogen formed is isolated from the alkali metal oxide by flowing out of the first reaction chamber 150 through the first gas outlet 154. Thereafter, according to some embodiments, the temperature within the first reaction chamber 150 is adjusted to temperature Tf(e.g., using the first heater 116) and vacuum pressure Pfinduce a decomposition of the alkali metal oxide into a recycled alkali metal and oxygen. According to some embodiments, the recycled alkali metal and oxygen are then vacuumed (e.g., using the second vacuum source 146) through the first intermediate opening 156, the intermediate tube 132 and the second intermediate opening 176 towards the second reaction chamber 170. According to some embodiments, the recycled alkali metal is then condensing in the second reaction chamber 170 and the oxygen is pumped out of the second reaction chamber 170.

[0345] The first repeat (i.e., the second cycle) of steps (a) to (g) is performed is the opposite direction, according to some embodiments. Thus, in the second cycle, the alkali metal begins within the second reaction chamber 170 and is recycled to the first reaction chamber 150.

[0346] Specifically, in the second cycle, according to some embodiments, a gas mixture comprising inert gas and water vapor is provided through the second gas mixture inlet 172 to the second reaction chamber 170, where a reaction between the water vapor and the recycled alkali metal takes place to form hydrogen and a mixture of the alkali metal and alkali metal hydroxide. Then, according to some embodiments, the hydrogen formed is optionally isolated by flowing out of the second reaction chamber 170 through the second gas outlet 174. Thereafter, according to some embodiments, the temperature within the second reaction chamber 170 is adjusted to temperature Td(e.g., using the second heater 118) to induce a reaction between the alkali metal and alkali metal hydroxide within the second reaction chamber 170, thereby forming hydrogen and an alkali metal oxide therein. Then, according to some embodiments, the hydrogen formed is isolated from the alkali metal oxide by flowingout of the second reaction chamber 170 through the second gas outlet 174. Thereafter, according to some embodiments, the temperature within the second reaction chamber 170 is adjusted to temperature Tf(e.g., using the second heater 118) and vacuum pressure Pfinduce a decomposition of the alkali metal oxide into a recycled alkali metal and oxygen. According to some embodiments, the recycled alkali metal and oxygen are then vacuumed (e.g., using the first vacuum source 144) through the second intermediate opening 176, the intermediate tube 132 and the first intermediate opening 156 towards the first reaction chamber 150. According to some embodiments, the recycled alkali metal is then condensing in the first reaction chamber 150 and the oxygen is pumped out of the first reaction chamber 150.

[0347] Thus, according to some embodiments, any cycle 2i, wherein i is an integer (e.g., cycles 2, 4, 6, 8 etc.) may be performed in conditions similar to the conditions of the 2ndcycle. According to some embodiments, any cycle 2i+l (e.g., cycles 3, 5, 7, 9 etc.), may be performed in conditions similar to the conditions of the 1stcycle.

[0348] According to some embodiments, repeating steps (a) to (g) at least once comprises performing steps (a2) to (g2).

[0349] Steps (a2) to (g2) will be described herein briefly and generally. However, more particular embodiments relating to each one of steps (a2) to (g2) can be appreciated by the person having ordinary skill in the art based on the more detailed description of the corresponding steps (a) to (g) above. Similarly, further cycles of the present process may include steps (a3) to (g3), steps (a4) to (g4), etc., their particulars can also be appreciated by the person having ordinary skill in the art based on the more detailed description of the corresponding steps (a) to (g) above.

[0350] According to some embodiments, step (a2) comprises providing an additional gas mixture comprising water vapor and an inert gas. According to some embodiments, step (a2) comprises providing the inert gas to the gas mixture from the inert gas source 104. According to some embodiments, step (a2) comprises providing the water vapor to the gas mixture from the water source 102. According to some embodiments, the particular composition of the additional gas mixture is as described for the gas mixture of step (a). According to some embodiments, providing the gas mixture in step (a2) further comprises switching the gas mixture inlet valve 110 to anopen state. According to some embodiments, providing the gas mixture in step (a2) further comprises switching the second gas inlet valve 114 to an open state.

[0351] According to some embodiments, step (b2) comprises flowing the additional gas mixture through the second gas inlet 172 into the second reaction chamber 170, thereby contacting the water with the recycled alkali metal and forming hydrogen and a mixture of the excess alkali metal and alkali metal hydroxide. According to some embodiments, the contacting of step (b2) in conducted within the second reaction chamber 170. According to some embodiments, step (b2) comprises flowing the gas mixture into the second reaction chamber 170. According to some embodiments, step (b2) comprises flowing the gas mixture through the second gas mixture inlet tube 108 into the second reaction chamber 170. According to some embodiments, step (b2) comprises flowing the gas mixture through the second gas mixture inlet 172 into the second reaction chamber 170. According to some embodiments, step (b2) comprises flowing the gas mixture from the water source and / or inert gas source through the second gas mixture inlet tube 108 into the second reaction chamber 170. According to some embodiments, step (b2) comprises flowing the gas mixture from the water source and / or inert gas source through the second gas mixture inlet 172 into the second reaction chamber 170. According to some embodiments, step (b2) comprises flowing the gas mixture from the water source and inert gas source through the second gas mixture inlet tube 108 into the second reaction chamber 170. According to some embodiments, step (b2) comprises flowing the gas mixture from the water source and inert gas through the second gas mixture inlet 172 into the second reaction chamber 170. According to some embodiments, step (b3) further comprises switching the second gas inlet valve 114 to an open state.

[0352] According to some embodiments, step (b2) further comprises monitoring the transformation of the alkali metal into the alkali metal hydroxide. According to some embodiments, the monitoring is carried out using the second detector 122. According to some embodiments, step (b2) further comprises stopping the flow of the gas mixture into the second reaction chamber 170 when the molar ratio as specified herein is reached. According to some embodiments, the second detector 122 is in functional communication with the second gas inlet valve 114, so that upon detection a predetermined conversion of alkali metal to alkali metal hydroxide, the second gas inlet valve 114 is automatically switched to a closed state.

[0353] According to some embodiments, steps (a2) and (b2) are performed simultaneously and Tbof step (b2) is substantially equal to Taof step (a2).

[0354] Specific embodiments of steps (a2) and (b2) are shown in Figure 3 (identifier 1) and Figure 4E. Specifically, Figure 3 and Figure 4E relate to particular embodiments, wherein the alkali metal is sodium.

[0355] According to some embodiments, step (c2) comprises, optionally, flowing the hydrogen formed in step (b2), the inert gas and optionally water vapor through the second gas outlet 174, thereby isolating the hydrogen produced in step (b2) from the mixture of the alkali metal and alkali metal hydroxide.

[0356] According to some embodiments, step (c2) comprises flowing the formed hydrogen, the inert gas and optionally water vapor through the second gas outlet 174. According to some embodiments, flowing gas through the second gas outlet 174 maintains a predetermined pressure Pcwithin the second reaction chamber 170.

[0357] With respect to pressures and temperatures specified herein, it is to be understood that the values provided refer to each cycle individually, wherein the values may repeat or be different between different cycles. For example, according to some embodiments, Pcis in the range of 0.7 Bar to 1.5 Bar and may be performed at 1 Bar in step (c) and at 1.1 Bar at step (c2).

[0358] According to some embodiments, step (2c) further comprises further isolating the hydrogen from the inert gas and optionally water vapor, wherein the further hydrogen isolation is performed using the gas separation unit 148. According to some embodiments, step (c2) further comprises analyzing the hydrogen using the hydrogen analyzer 149.

[0359] According to some embodiments, steps (a2), (b2) and (c2) are performed at least partially simultaneously. According to some embodiments, steps (a2), (b2) and (c2) are performed simultaneously and Ta, Tband Tcthereof are substantially equal.

[0360] Specific embodiments of step (c2) are shown in Figure 3 (identifier 5) and Figure 4E. Specifically, Figure 3 and Figure 4E relate to particular embodiments, wherein the alkali metal is sodium.

[0361] According to some embodiments, step (d2) comprises switching the second gas inlet valve 114 to a closed state and adjusting the temperature of the mixture of step(b2) to the temperature Td, thereby forming hydrogen and the alkali metal oxide. According to some embodiments, the contacting of step (d2) in conducted within the second reaction chamber 170.

[0362] According to some embodiments, step (d2) comprises applying heat to the alkali metal and the alkali metal hydroxide. According to some embodiments, step (d2) comprises applying heat to the second reaction chamber 170 by the second heater 118. According to some embodiments, applying heat comprises application of induction heating. According to some embodiments, step (d2) comprises switching the second gas inlet valve 112 to a closed state; and adjusting the temperature of the second reaction chamber 170 to the temperature Tdusing the second heater 118, thereby forming hydrogen and the alkali metal oxide.

[0363] Specific embodiments of step (d2) are shown in Figure 3 (identifier 2) and Figure 4F. Specifically, Figure 3 and Figure 4F relate to particular embodiments, wherein the alkali metal is sodium.

[0364] According to some embodiments, step (e2) comprises flowing the hydrogen formed in step (d2) and optionally, the hydrogen produced in step (b2) through the second gas outlet 174, wherein the second gas outlet valve 128 is in an open state, thereby isolating the hydrogen produced in step (d2) and optionally, the hydrogen produced in step (b2) from the alkali metal oxide, which remains within the second reaction chamber 170. According to some embodiments, flowing gas through the second gas outlet 174 results in a predetermined pressure Pewithin the second reaction chamber 170.

[0365] According to some embodiments, steps (d2) and (e2) are performed at least partially simultaneously. According to some embodiments, steps (d2) and (e2) are performed simultaneously and Pdof step (d2) is substantially equal to Peof step (e2). According to some embodiments, steps (d2) and (e2) are performed simultaneously and Tdof step (d2) is substantially equal to Teof step (e2).

[0366] According to some embodiments, step (e2) further comprises further isolating the hydrogen from the inert gas and optionally water vapor using the gas separation unit 148. According to some embodiments, step (e2) further comprises analyzing the hydrogen using the hydrogen analyzer 149.

[0367] According to some embodiments, step (e2) comprises flowing the hydrogen, the inert gas and optionally water vapor through the second gas outlet 174, wherein the second gas outlet valve 130 is in an open state, thereby isolating the hydrogen from the alkali metal oxide, which remains within the second reaction chamber 170.

[0368] Specific embodiments of step (e2) are shown in Figure 3 (identifier 6) and Figure 4F. Specifically, Figure 3 and Figure 4F relate to particular embodiments, wherein the alkali metal is sodium.

[0369] According to some embodiments, step (f2) comprises switching each of the first gas inlet valve 112 and second gas inlet valve 114 to a closed state. According to some embodiments, step (f2) comprises switching the intermediate tube valve 134 to an open state to form fluid communication between the first reaction chamber 150 and the second reaction chamber 170. According to some embodiments, step (f2) comprises connecting the first vacuum opening 158 to a first vacuum source 144. According to some embodiments, step (f2) comprises applying vacuum using the first vacuum source 144, so that the pressure within the first reaction chamber 150 and second reaction chamber 170 is Pf, as defined herein. According to some embodiments, step (f2) comprises adjusting the second reaction chamber 170 to temperature Tfto induce decomposition of the alkali metal oxide into a recycled alkali metal and oxygen.

[0370] According to some embodiments, step (f2) comprises switching the first gas inlet valve 112 to a closed state. According to some embodiments, step (f2) comprises switching the second gas inlet valve 114 to a closed state. According to some embodiments, step (f2) comprises switching the second gas outlet valve 130 to a closed state. According to some embodiments, step (f2) comprises switching the first vacuum valve 140 to an open state. According to some embodiments, step (f2) comprises applying vacuum using the first vacuum source 144. According to some embodiments, step (f2) comprises applying vacuum to the second reaction chamber 170 using the first vacuum source 144. According to some embodiments, step (f2) comprises applying vacuum to the first reaction chamber 150 using the first vacuum source 144. Specifically, according to some embodiments, in step (f2) vacuum is applied using the first vacuum source 144. According to some embodiments, the applied vacuum creates suction through the first vacuum tube 136. According to some embodiments, the applied vacuum creates suction through the first vacuum opening 158. According tosome embodiments, the vacuum applied to the first vacuum opening 158 creates vacuum within the first reaction chamber 150. According to some embodiments, the applied vacuum creates suction through the first intermediate opening 156. According to some embodiments, the applied vacuum creates suction through the intermediate tube 132. According to some embodiments, the applied vacuum creates suction through the second intermediate opening 176. According to some embodiments, the vacuum applied to the second intermediate opening 176 creates vacuum within the second reaction chamber 170.

[0371] According to some embodiments, step (f2) comprises applying heat to the second reaction chamber 170 by the second heater 118. According to some embodiments, applying heat comprises application of induction heating.

[0372] Specific embodiments of step (f2) are shown in Figure 3 (identifier 3) and Figure 4G. Specifically, Figure 3 and Figure 4G relate to particular embodiments, wherein the alkali metal is sodium.

[0373] According to some embodiments, step (g2) comprises adjusting the first reaction chamber 150 to the temperature Tg2and the second reaction chamber 170 to the temperature Tgl. According to some embodiments, step (g2) comprises applying vacuum using the first vacuum source 144, so that the pressure within the first reaction chamber 150 and second reaction chamber 170 is Pg, as detailed herein. According to some embodiments, step (g2) comprises vacuum distilling the alkali metal and condensing it in the first reaction chamber 150.

[0374] According to some embodiments, step (g2) comprises flowing the formed recycled alkali metal and oxygen through the second intermediate opening 176 by vacuum suction. According to some embodiments, step (g2) comprises flowing the formed recycled alkali metal and oxygen through the second intermediate opening 176, the intermediate tube 132 and the first intermediate opening 156 by vacuum suction using the first vacuum source 144. According to some embodiments, step (g2) comprises evaporating the recycled alkali metal in the second reaction chamber 170. According to some embodiments, step (g2) comprises condensing the recycled alkali metal in the first reaction chamber 150.

[0375] Specific embodiments of step (g2) are shown in Figure 3 (identifiers 4 and 7) and Figure 4H. Specifically, Figure 3 and Figure 4H relate to particular embodiments, wherein the alkali metal is sodium.

[0376] Although the invention is described in conjunction with specific embodiments thereof, it is evident that numerous alternatives, modifications and variations that are apparent to those skilled in the art may exist. It is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and / or methods set forth herein. Other embodiments may be practiced, and an embodiment may be carried out in various ways. Accordingly, the invention embraces all such alternatives, modifications and variations that fall within the scope of the appended claims.

Claims

CLAIMS1. A process for water splitting, the process comprising:(a) providing a gas mixture comprising water vapor and an inert gas;(b) contacting the gas mixture with an alkali metal, to form hydrogen and a mixture of the alkali metal (MA) and alkali metal hydroxide (MA0H);(c) optionally, isolating the hydrogen produced in step (b) from the mixture of the alkali metal and alkali metal hydroxide;(d) adjusting the temperature of the mixture of step (b) to a temperature Td, which is in the range of 100°C to 600°C to induce a reaction between the alkali metal and alkali metal hydroxide, thereby forming hydrogen and an alkali metal oxide (MA2O);(e) isolating the hydrogen produced in step (d), and optionally, the hydrogen produced in step (b) from the alkali metal oxide;(f) adjusting the alkali metal oxide formed in step (e) to a temperature Tf, which is in the range of 400°C to 1000°C and a pressure Pfin the range of 0.1 torr to 100 torr, to induce a decomposition of the alkali metal oxide into a recycled alkali metal and oxygen;(g) isolating the recycled alkali metal produced in step (f), wherein the process further comprises repeating steps (a) to (g) at least once, by reusing the recycled alkali metal isolated in step (f) for subsequent use in repeated step (b).

2. The process according to claim 1, wherein the gas mixture of step (a) comprises water vapor at a relative humidity of 10% to 100% in the inert gas.

3. The process according to claim 2, wherein the relative humidity is in the range of 50% to 100%.

4. The process according to claim 1, wherein the gas mixture of step (a) comprises 1.2% to 3.2% water vapor v / v in the inert gas.

5. The process according to any one of claims 1 to 4, wherein step (a) comprises providing an aqueous salt solution and flowing an inert gas over or through the aqueous salt solution, thereby forming the gas mixture.

6. The process according to claim 5, wherein the aqueous salt solution is a saturated aqueous salt solution.

7. The process according to any one of claims 5 to 6, wherein the salt is selected from the group consisting of ammonium nitrate, ammonium sulfate, magnesium chloride, magnesium nitrate, lithium chloride, potassium sulfate, potassium nitrate, potassium chloride, potassium acetate, potassium hydroxide, sodium chloride, sodium nitrite, sodium dichromate and combinations thereof.

8. The process according to any one of claims 1 to 7, wherein the gas mixture provided in step (a) comprises steam and the inert gas.

9. The process according to claim 8, wherein the steam is superheated steam.

10. The process according to any one of claims 1 to 9, wherein the gas mixture provided in step (a) is substantially devoid of water aerosol.

11. The process according to any one of claims 1 to 10, wherein the gas mixture is provided in step (a) at a temperature Tain the range of 5°C to 600°C.

12. The process according to claim 11, wherein temperature Tais in the range of 15°C to 40°C.

13. The process according to any one of claims 1 to 12, wherein the alkali metal of step (b) is sodium.

14. The process according to any one of claims 1 to 13, wherein step (b) comprises contacting the water within the gas mixture with the alkali metal, wherein the alkali metal is in a molar excess over the contacted water.

15. The process according to claim 14, wherein the molar ratio between the alkali metal and the contacted water is in the range of 1.5:1 to 2.5:1.

16. The process according to any one of claims 1 to 15, wherein step (b) comprises flowing the gas mixture into a first reaction chamber of a reactor, the first reaction chamber contains the alkali metal, at a flow rate and time period thatresults in a molar ratio between the alkali metal and the water reacting therewith to be in the range of 1.75:1 to 2.25:1, to induce the following reaction:0.5 H2(g), thereby forming the hydrogen and the mixture of the excess alkali metal and alkali metal hydroxide.

17. The process according to claim 16, wherein step (b) further comprises monitoring the transformation of the alkali metal into the alkali metal hydroxide, and to stop flowing the gas mixture into the first reaction chamber when the molar ratio is reached.

18. The process according to any one of claims 16 to 17, wherein the first reaction chamber comprises a first gas inlet and a first gas outlet, wherein step (b) comprises: flowing the gas mixture through the first gas inlet into the first reaction chamber to contact the alkali metal, induce the reaction and form the hydrogen and the mixture of the excess alkali metal and alkali metal hydroxide; and flowing the formed hydrogen, the inert gas and optionally water vapor through the first gas outlet, thereby maintaining a pressure Pbwithin the first reaction chamber.

19. The process according to any one of claims 1 to 18, wherein step (b) is performed at a pressure Pbof about 1 Bar.

20. The process according to any one of claims 1 to 19, wherein step (b) is performed at a temperature Tbin the range of 5 °C to 600°C.

21. The process according to claim 20, wherein temperature Tbis in the range of 15°C to 40°C.

22. The process according to any one of claims 1 to 21, comprising isolating the hydrogen produced in step (b) from the mixture of the alkali metal and alkali metal hydroxide in step (c).

23. The process according to any one of claims 1 to 22, whereinstep (b) comprises: providing a reactor contains the alkali metal and comprises a first reaction chamber, the first reaction chamber comprising a first gas inlet and a first gas outlet, and flowing the gas mixture through the first gas inlet into the first reaction chamber, thereby contacting the water with the alkali metal and forming the hydrogen and the mixture of the excess alkali metal and alkali metal hydroxide; and step (c) comprises flowing the formed hydrogen, the inert gas and optionally water vapor through the first gas outlet, thereby isolating the hydrogen produced in step (b) from the mixture of the alkali metal and alkali metal hydroxide.

24. The process according to claim 23, wherein step (c) further comprises further isolating the hydrogen from the inert gas and optionally water vapor flown through the first gas outlet.

25. The process according to claim 24, wherein the further hydrogen isolation comprises condensing the inert gas and optionally water vapor and recovering the hydrogen gas.

26. The process according to any one of claims 1 to 25, wherein step (d) is performed substantially in the absence of water.

27. The process according to any one of claims 1 to 26, wherein step (d) is performed under inert gas.

28. The process according to any one of claims 1 to 27, wherein step (d) is performed at a pressure Pdin the range of 0.9 Bar to 2 Bar.

29. The process according to any one of claims 1 to 28, wherein step Tdis in the range of 320°C to 400°C.

30. The process according to any one of claims 1 to 29, wherein step (b) comprises: providing a reactor comprising:a first reaction chamber, which contains the alkali metal and comprises a first gas inlet and a first gas outlet; a first gas inlet valve, configured to monitor gas flow through the first gas inlet into the first reaction chamber, and a first gas outlet valve, configured to monitor fluid flow through the first gas outlet out of the first reaction chamber; flowing the gas mixture through the first gas inlet into the first reaction, wherein the first gas inlet valve is in an open state, thereby contacting the water with the alkali metal and forming the hydrogen and the mixture of the excess alkali metal and alkali metal hydroxide; and step (d) comprises switching the first gas inlet valve to a closed state; and adjusting the temperature of the mixture of step (b) to the temperature Td, thereby forming hydrogen and the alkali metal oxide.

31. The process according to claim 30, comprising step (c) of: flowing the hydrogen formed in step (b), the inert gas and optionally water vapor through the first gas outlet, wherein the first gas outlet valve is in an open state, thereby isolating the hydrogen produced in step (b) from the mixture of the alkali metal and alkali metal hydroxide, which remains within the first reaction chamber.

32. The process according to any one of claims 30 to 31, wherein step (e) comprises flowing the hydrogen formed in step (d) and optionally, the hydrogen produced in step (b) through the first gas outlet, wherein the first gas outlet valve is in an open state, thereby isolating the hydrogen produced in step (d) and optionally, the hydrogen produced in step (b) from the alkali metal oxide, which remains within the first reaction chamber.

33. The process according to any one of claims 1 to 32, wherein step (e) further comprises further isolating the hydrogen from residual inert gas and optionally water vapor.

34. The process according to claim 33, wherein the further hydrogen isolation comprises condensing the inert gas and optionally water vapor and recovering the hydrogen gas.

35. The process according to any one of claims 1 to 34, wherein step (f) is performed substantially in the absence of water and hydrogen.

36. The process according to any one of claims 1 to 35, wherein step (f) is performed under vacuum.

37. The process according to any one of claims 1 to 36, wherein step (f) is performed at a pressure Pfin the range of 0.1 torr to 5 torr.

38. The process according to any one of claims 1 to 36, wherein temperature Tf, is in the range of 500°C to 600°C.

39. The process according to any one of claims 30 to 32, wherein the first reaction chamber further comprises a first intermediate opening and a first vacuum opening, and the reactor further comprises: a second reaction chamber, which comprises a second gas inlet, a second gas outlet, a second intermediate opening and a second vacuum opening; a second gas inlet valve, configured to monitor gas flow through the second gas inlet into the first reaction chamber, and a second gas outlet valve, configured to monitor gas flow through the second gas outlet out of the second reaction chamber; an intermediate tube connecting the first intermediate opening and the second intermediate opening; and an intermediate tube valve, configured to monitor fluid flow through the intermediate tube; wherein step (f) comprises: switching each of the first gas inlet valve and second gas inlet valve to a closed state; switching the intermediate tube valve to an open state to form fluid communication between the first reaction chamber and the second reaction chamber;connecting the second vacuum opening to a second vacuum source; applying vacuum using the second vacuum source, so that the pressure within the first reaction chamber and second reaction chamber, Pf, is in the range of 0.1 torr to 100 torr; and adjusting the first reaction chamber to temperature Tfto induce the decomposition.

40. The process according to any one of claims 1 to 39, wherein step (g) comprises isolating the recycled alkali metal produced in step (f) by vacuum distillation.

41. The process according to any one of claims 1 to 40, wherein step (g) is performed at a pressure Pgin the range of 0.1 torr to 5 torr.

42. The process according to claim 39, wherein step (g) comprises adjusting the first reaction chamber to temperature Tgl; adjusting the second reaction chamber to temperature Tg2, which is at least 100°C lower than Tgl; and applying vacuum using the second vacuum source, so that the pressure within the first reaction chamber and second reaction chamber, Pg, is in the range of 0.5 torr to 5 torr, wherein the alkali metal is solid or liquid at Tg2and Pgand at least partially vaporizes at Tgland Pg, thereby vacuum distilling the alkali metal and condensing it in the second reaction chamber.

43. The process according to claim 42, wherein Pgis substantially equal to Pf, and wherein steps (g) and (f) are performed simultaneously.

44. The process according to any one of claims 42 to 43, wherein temperature Tgl, is in the range of 500°C to 600°C.

45. The process according to any one of claims 42 to 44, wherein temperature Tg2, is in the range of 5°C to 40°C.

46. The process according to any one of claims 1 to 45, wherein adjusting the temperature in each one of steps (d) and (f) comprises applying induction heating.

47. The process according to any one of claims 42 to 45, wherein repeating steps (a) to (g) at least once comprises:(a2) providing an additional gas mixture comprising water vapor and an inert gas;(b2) flowing the additional gas mixture through the second gas inlet into the second reaction chamber, thereby contacting the water with the recycled alkali metal and forming hydrogen and a mixture of the excess alkali metal and alkali metal hydroxide(c2) optionally, flowing the hydrogen formed in step (b2), the inert gas and optionally water vapor through the second gas outlet, thereby isolating the hydrogen produced in step (b2) from the mixture of the alkali metal and alkali metal hydroxide;(d2) switching the second gas inlet valve to a closed state and adjusting the temperature of the mixture of step (b2) to the temperature Td, induce a reaction between the alkali metal and alkali metal hydroxide thereby forming hydrogen and the alkali metal oxide;(e2) flowing the hydrogen formed in step (d2) and optionally, the hydrogen produced in step (b2) through the second gas outlet, wherein the second gas outlet valve is in an open state, thereby isolating the hydrogen produced in step (d2) and optionally, the hydrogen produced in step (b2) from the alkali metal oxide, which remains within the second reaction chamber.(f2) switching each of the first gas inlet valve and second gas inlet valve to a closed state, switching the intermediate tube valve to an open state to form fluid communication between the first reaction chamber and the second reaction chamber; connecting the first vacuum opening to a first vacuum source; applying vacuum using the first vacuum source, so that the pressure within the first reaction chamber and second reaction chamber, Pf, is in the range of 0.1 torr to 100 torr; andadjusting the second reaction chamber to temperature Tfto induce decomposition of the alkali metal oxide into a recycled alkali metal and oxygen;(g2) adjusting the first reaction chamber to the temperature Tg2and the second reaction chamber to the temperature Tgl; and applying vacuum using the first vacuum source, so that the pressure within the first reaction chamber and second reaction chamber, Pg, is in the range of 0.5 torr to 5 torr, thereby vacuum distilling the alkali metal and condensing it in the first reaction chamber.

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