EP-4735668-A1 - MULTI-PHASE REACTOR FOR HYDROGEN PRODUCTION

Abstract

The disclosure provides a method of producing hydrogen. The method comprises conducting a thermochemical reaction by contacting an active reagent and a basic aqueous solution, to thereby cause water from the basic aqueous solution to react with the active reagent and to produce hydrogen and a basic aqueous solution comprising an oxidised product. The method further comprises disposing the basic aqueous solution comprising the oxidised product in an electrochemical cell comprising an anode and a cathode, such that at least a portion of the cathode contacts the solution; and conducting an electrochemical reaction by applying a voltage across the anode and the cathode to produce hydrogen, oxygen and the active reagent. The active reagent comprises a metal or metal ion in a first oxidation state and the oxidised product comprises the metal or metal ion in a second oxidation state which is higher than the first oxidation state.

Inventors

• AMINI HORRI, BAHMAN

Assignees

• Clean Hydrogen Limited

Dates

Publication Date

20260506

Application Date

20240627

Claims (20)

1. Claims 1. A method of producing hydrogen, the method comprising: - conducting a thermochemical reaction by contacting an active reagent and a basic aqueous solution, to thereby cause water from the basic aqueous solution to react with the active reagent and to produce hydrogen and a basic aqueous solution comprising an oxidised product; - disposing the basic aqueous solution comprising the oxidised product in an electrochemical cell comprising an anode and a cathode, such that at least a portion of the cathode contacts the solution; and - conducting an electrochemical reaction by applying a voltage across the anode and the cathode to produce hydrogen, oxygen and the active reagent; wherein the active reagent comprises a metal or metal ion in a first oxidation state and the oxidised product comprises the metal or metal ion in a second oxidation state which is higher than the first oxidation state.
2. 2. A method of producing hydrogen, the method comprising: - disposing a basic aqueous solution comprising an oxidised product in an electrochemical cell comprising an anode and a cathode, such that at least a portion of the cathode contacts the solution; - conducting an electrochemical reaction by applying a voltage across the anode and the cathode to produce hydrogen, oxygen and an active reagent; and - conducting a thermochemical reaction by contacting the active reagent and a basic aqueous solution, to thereby cause water from the basic aqueous solution to react with the active reagent and to produce hydrogen and a basic aqueous solution comprising an oxidised product, wherein the active reagent comprises a metal or metal ion in a first oxidation state and the oxidised product comprises the metal or metal ion in a second oxidation state which is higher than the first oxidation state.
3. 3. The method according to claim 1 or claim 2, wherein the electrochemical reaction is conducted continuously.
4. 4. The method according to any preceding claim, wherein the thermochemical reaction is conducted continuously.
5. 5. The method according to any preceding claim, wherein the active reagent is or comprises a transition metal or an alloy thereof, a p-block metal or an alloy thereof or a reactivated spinel/perovskite composite with multiple oxidation states.
6. 6. The method according to claim 5, wherein the active reagent is or comprises a transition metal or an alloy thereof or a p-block metal or an alloy thereof, and the p- block metal, or the alloy thereof, is selected from the group consisting of tin, lead, thallium, selenium and bismuth and the transition metal, or the alloy thereof, is selected from the group consisting of zinc, copper, iron, nickel, cobalt, manganese, titanium, molybdenum, cadmium, chromium, vanadium, silver, rhodium, platinum, palladium, iridium, osmium, rhenium, ruthenium, lanthanum and zirconium.
7. 7. The method according to claim 6, wherein the active reagent is or comprises a transition metal or an alloy thereof and is zinc.
8. 8. The method according to claim 5, wherein the active reagent is or comprises a reactivated spinel/perovskite composite with multiple oxidation states having general formula Zn x M y O z , where Zn is zinc, M is a metal, O is oxygen and x, y and z are each an integer between 1 and 10, and the metal is a transition metal or a p-block metal.
9. 9. The method according to any preceding claim, wherein the method comprises contacting the active reagent and the basic aqueous solution in the presence of a catalyst.
10. 10. The method according to claim 10, wherein the catalyst comprises or is iron(III) oxide (Fe 2 O 3 ), nickel hydroxide (Ni(OH) 2 ), potassium stannate (K 2 SnO 3 ), copper hydroxide (Cu(OH) 2 ), or combinations thereof, and is preferably iron(III) oxide (Fe 2 O 3 ).
11. 11. The method according to any preceding claim, wherein the thermochemical reaction is conducted at an elevated temperature of less than 700°C, less than 650°C, less than 600°C, less than 550°C, less than 500°C, less than 450°C, less than 400°C, less than 300°C, less than 250°C, less than 200°C, less than 175°C, less than 160°C or less than 150°C. .
12. 12. The method according to any preceding claim, wherein the thermochemical reaction produces a gas stream comprising hydrogen and steam, and the method comprises cooling the gas stream produced in the thermochemical reaction to cause water to condense out of the gas stream.
13. 13. The method according to claim 12, wherein cooling the gas stream comprises transferring heat from the gas stream to a cooling fluid, and the cooling fluid is or comprises water, and is subsequently be used in the thermochemical reaction.
14. 14. The method according to any preceding claim, wherein during the thermochemical reaction, the active reagent is suspended in the basic aqueous solution.
15. 15. The method according to any preceding claim, wherein the basic aqueous solution comprises a base at a concentration of between 0.5 and 50 M, between 1 and 45 M, between 2 and 40 M, between 4 and 35 M, between 6 and 30 M, or between 8 and 28 M.
16. 16. The method according to claim 13, wherein the method may comprises adding water to the basic aqueous solution to maintain a desired concentration of the base in the basic aqueous solution and/or a desired pH of the basic aqueous solution.
17. 17. An apparatus for producing hydrogen, the apparatus comprising: - a thermochemical reactor, configured to hold a basic aqueous solution and an active reagent therein and thereby allow a thermochemical reaction to proceed and produce a gas stream comprising hydrogen and a basic aqueous solution comprising an oxidised product; - an electrochemical cell comprising an anode and a cathode, and configured to receive the basic aqueous solution comprising the oxidised product from the thermochemical reactor, such that at least a portion of the cathode contacts the basic aqueous solution comprising the oxidised product, the electrochemical cell being configured to cause an electrochemical reaction to proceed and produce hydrogen gas and the active reagent at the cathode and oxygen at the anode; - a first conduit extending between the thermochemical reactor and the electrochemical cell, the first conduit being configured to feed the basic aqueous solution comprising the oxidised product from the thermochemical reactor to the electrochemical cell; and - a second conduit extending between the thermochemical reactor and the electrochemical cell, the second conduit being configured to feed the basic aqueous solution and the active reagent from the electrochemical cell to the thermochemical reactor.
18. 18. The apparatus according to claim 17, wherein the thermochemical reactor comprises an agitator configured to agitate the basic aqueous solution in the thermochemical reactor.
19. 19. The apparatus according to claim 17 or claim 18, wherein the apparatus comprises a condenser configured to cool the gas stream produced in the thermochemical reactor, and thereby cause water in the gas stream to condense.
20. 20. The apparatus according to any one of claims 17 to 19, wherein the apparatus comprises a heat exchanger, and the first and second conduits extend therethrough, wherein the heat exchanger is configured to transfer heat between the first and second conduits.

Description

Multi-Phase Reactor for Hydrogen Production The invention relates to a method of producing hydrogen gas. In particular embodiment of the invention, the method may be a sustainable cyclic process. The invention also extends to an apparatus for producing hydrogen gas. Hydrogen is an important energy carrier and has the potential to replace hydrocarbon based fuels for sustainable development. The current energy related problems with hydrocarbon fuels, such as air pollution, climate change and scarcity of the resource, are important motivations for exploring hydrogen. As an alternative fuel source, hydrogen has the highest specific energy content of all fuels, and can be used for clean power generation in fuel cells with limited or no net atmospheric emissions and is convenient for efficient energy storage. Hydrogen can be used directly as a transportation fuel yielding a higher energy efficiency which is receiving much favourable attention as a technical and political issue. Currently, several industrial methods of hydrogen production exist, and among these are reforming, photoconversion and electrolysis, which have gained prominence. Water electrolysis provides the cleanest solution for hydrogen production. Its advantages are (i) it gives zero carbon emissions; (ii) it produces pure hydrogen, influencing fuel cell technology which is heavily affected by impurities in the hydrogen feed; (iii) it is independent of hydrocarbon resources; (iv) it can be operated in small scale plants; and (v) renewable energy can be used to produce the hydrogen. WO 2020/016580 A2 describes a process which can be used to produce hydrogen in both an electrolytic process of water decomposition and a thermochemical reaction. The latter is carried out in an enclosed reactor where a metal, such as zinc, is reacted with steam at high temperature to produce hydrogen gas and a metal oxide. This method suffers from disadvantages including: (a) the method is difficult to run in a continuous mode since the solid metal has to be introduced to the thermochemical reactor chamber and the solid oxide product removed therefrom, and (b) during the thermochemical reaction, the metal surface quickly passivates with a layer of oxide, which retards the rate of hydrogen production. The present invention arose from our work in attempting to overcome the aforementioned problems associated with the prior art. We hereby disclose an invention enabling hydrogen production in a system which can operate in a continuous mode and is readily scalable. In accordance with a first aspect of the invention, there is provided a method of producing hydrogen, the method comprising: - conducting a thermochemical reaction by contacting an active reagent and a basic aqueous solution to produce hydrogen and a basic aqueous solution comprising an oxidised product; - disposing the basic aqueous solution comprising the oxidised product in an electrochemical cell comprising an anode and a cathode, such that at least a portion of the cathode contacts the solution; and - conducting an electrochemical reaction by applying a voltage across the anode and the cathode to produce hydrogen, oxygen and the active reagent; wherein the active reagent comprises a metal or metal ion in a first oxidation state and the oxidised product comprises the metal or metal ion in a second oxidation state which is higher than the first oxidation state. Advantageously, both the thermochemical and electrochemical reactions produce hydrogen. Additionally, both the thermochemical reaction and the electrochemical reaction occur in an aqueous solution. Accordingly, the solution can be readily circulated between a thermochemical reactor and the electrochemical cell without additional processing steps being required. Furthermore, since the thermochemical reaction is conducted in a solution, the oxidised product may dissolve as it is formed. Accordingly, the method overcomes the problem of passivation observed in the prior art and favours conversion of the active reagent into the oxidised product. By using an alkaline solutions and changing the reaction phase to the aqueous mode, the type of reactor can be simplified to a “hydrolyser” rather than a “fixed bed” reactor. Conducting the reaction step in an “aqueous phase” reaction mode offers a big advantage to the process operation by making it possible to run both the reactor and electrolyser in a “continuous” mode. In other words, the “hydrothermal reactor” and “the electrochemical cell” could be directly connected using a pump to recirculate a single liquid phase “basic aqueous solution” across these central units. The phrase “thermochemical reaction”, as recited herein may be replaced with the phrase “hydrothermal reaction”. Similarly, the phrase “thermochemical reactor” may be replaced by the phrase “hydrothermal reactor” or “hydrolyser”. It may be appreciated that the electrochemical reaction may be conducted before the thermochemical reaction. Accordingly