ELECTROLYTIC HYDROGEN PURIFICATION

Abstract

ELECTROLYTIC HYDROGEN PURIFICATION The present invention relates to a method for purifying a hydrogen stream contaminated by water, oxygen, and optionally nitrogen. The method comprises contacting the hydrogen stream to be purified with a zeolitic adsorbent material comprising at least one metal selected from the metals of columns 3 to 12 of the Periodic Table of Elements, in its zero-valence metallic form, or in its oxidized or reduced form, and recovering the purified hydrogen stream. The invention also relates to the use of a zeolitic adsorbent material comprising at least one metal from columns 3 to 12 of the Periodic Table of Elements for hydrogen purification, as well as the use of hydrogen thus purified in industrial processes. Fig.: None

Description

Description Title of the invention: PURIFICATION OF HYDROGEN ELECT- TROLYTIC

[0001] — The invention relates to a method for purifying hydrogen from an elect- trolyzer and more specifically a process for purifying hydrogen containing water and oxygen, as well as possibly traces of nitrogen and / or traces of residual electrolytes, such as potassium hydroxide.

[0002] — The vast majority of hydrogen produced industrially today is obtained by steam reforming. However, the ecological constraints linked to the re- Global warming has prompted scientists to reconsider electrolysis water to produce hydrogen. One of the disadvantages of water electrolysis is that the hydrogen produced contains different contaminants than that produced by steam reforming, and contains in particular oxygen, nitrogen and water.

[0003] Indeed, the hydrogen produced by electrolysis of water is often polluted by co-produced oxygen, particularly due to excessive permeation of oxygen to through the separating membrane(s) or solubilization of oxygen in the electrolyte. As for the water present in the hydrogen flow, this generally comes from usually from gaseous entrainments, while nitrogen comes for example from the phases inerting at the start of the electrolyser and its solubilisation in cold water and often under pressure introduced into the electrolyser.

[0004] — All of these contaminants must be eliminated because most or all uses hydrogen requires very pure gas, for example when hydrogen is used in the electrical or electronic field, particularly in fuel cells. In fact, in this type of use, contamination from 5 ppm of oxygen reduces the efficiency of the fuel cell. Furthermore, the possible presence of nitrogen (for example if the water used is poorly degassed) can affect the operation and power of a downstream fuel cell, It is therefore crucial to be able to have a very pure hydrogen.

[0005] — The prior art already provides numerous solutions for obtaining very high-quality hydrogen. pure. In particular, we can cite patent US11420869 B2 which describes the purification by PSA (abbreviation for “Pressure Swing Adsorption” in English or "Pressure Swing Adsorption") of a hydrogen stream containing hydro- carbides and oxygen. The flow to be purified thus contains, for example, methane, hydrocarbons C,—C+, as well as traces of nitrogen, carbon monoxide and oxygen. This could be, for example, flows from a dehydro- propane generation. Typically, hydrocarbon removal is carried out on activated carbon, oxygen and carbon monoxide are removed by catalytic reaction on a layer of copper-impregnated alumina, while water and CO; produced by the catalytic reaction are removed by another layer of activated carbon. Document US20190247781 A proposes to specifically remove oxygen using a catalyst based on palladium (Pd), platinum (Pt) or copper (Cu) on alumina to reduce oxygen, before purification on PSA (so-called “DEOXO” unit). Furthermore, Ligen et al, “Energy efficient hydrogen drying and purification for fuel cell vehicles”, Int. J. Hydrogen Energy, (2020), 45, 10639 sqq., detail the use of a combination of DEOXO + VPSA (“Volume and Pressure Swing Adsorption”) units to purify a hydrogen stream from an alkaline electrolyzer. However, one of the disadvantages of prior art techniques is that oxygen adsorbs only weakly, or even very weakly, on most of the adsorbents conventionally used in PSA Hydrogen techniques, namely activated carbons, aluminas, silica gels, molecular sieves of type 5A or 13X. Thus, and in order to remove oxygen from a hydrogen matrix, the solution adopted to date by the industry is to use a DEOXO unit which reduces the oxygen to water, typically with a copper-impregnated alumina. The water is then removed in a PSA drying process. In conclusion, in order to purify a hydrogen matrix containing oxygen, no less than two units are required, which generates significant installation and energy costs. Document US2021309517 A1 describes a purification process by adsorption on a bed consisting of at least one layer of oxygen reduction catalyst based on supported Cu, Pd or Pt, catalyst which is regenerated by countercurrent circulation of a hydrogen-rich gas free of any oxygen by PSA process or by TSA (Temperature Swing Adsorption) process. The preferred catalyst is an alumina impregnated with at least 10% by mass of copper. It is preferably used in three layers: a first layer of adsorbent dries the flow (silica gel, activated alumina, 13X), a second layer (copper-impregnated alumina) removes the oxygen by exothermic catalytic reaction (0; + H, HzO), the third layer (silica gel, activated alumina, 13X, CaX, SA) removes the water produced during the passage of the flow over the second layer as well as possibly the nitrogen. This solution, consisting of a single treatment bed with several layers of materials (adsorbents and catalyst), represents progress, but involves a certain complexity and a high cost linked to the use of several materials and a catalyst based on alumina heavily loaded with copper. There remains a need for an easily in- industrializable, less expensive and easy to implement, in particular a hydrogen purification process that is less expensive and easier to implement than with the techniques known today. Thus, one of the objectives of the present invention is to provide a hydrogen purification process that makes it possible to overcome the drawbacks encountered in the prior art, and in particular to purify hydrogen more easily, and in particular to eliminate both the oxygen and the water present as impurities in a hydrogen stream. Another objective of the present invention is to provide a hydrogen purification method making it possible to eliminate both oxygen and water present as impurities in a hydrogen stream, but also nitrogen as well as other impurities such as traces of residual electrolytes, such as for example potassium hydroxide, in particular for hydrogen streams originating from an electrolyser, also called electrolytic hydrogen. Still other objectives will become apparent in the light of the description of the present invention which follows. The Applicant has now discovered that it is possible to meet in full or at least in part the objectives set out above and in particular to purify a hydrogen stream, in particular an electrolytic hydrogen stream, by eliminating, or at least significantly reducing, the oxygen and water contents, as well as, where appropriate, the nitrogen contents and other traces of residual electrolytes, in a simple, effective and relatively inexpensive manner, and in particular by overcoming in full or in part the problems encountered in the prior art. The present invention thus proposes an “all-in-one” process for purifying hydrogen, by eliminating oxygen and water using a single zeolitic adsorbent material, the zeolite of which has undergone at least a partial cation exchange and / or impregnation with at least one metal from columns 3 to 12 of the Periodic Table of Elements. More specifically, the present invention relates to a method for purifying a hydrogen stream containing water, oxygen and optionally nitrogen, comprising: - at least one step of bringing the hydrogen stream to be purified into contact with a zeolitic adsorbent material comprising at least one metal from columns 3 to 12 of the Periodic Table of Elements, in metallic form of zero valence, or in oxidized form or in reduced form, and - at least one step of recovery of purified hydrogen flow. In one embodiment of the invention, the hydrogen to be purified comprises electrolytic hydrogen, i.e. hydrogen obtained by electrolysis of water. In a preferred embodiment, the hydrogen to be purified comprises mainly hydrogen, i.e. from 60 mol% to 99.99 mol% of pure hydrogen, preferably from 80 mol% to 99.99 mol% of pure hydrogen, more preferably from 90 mol% to 99.99 mol% of pure hydrogen and more preferably from 95 mol% to 99.99 mol% of pure hydrogen, typically from 96.50 mol% to 99.99 mol% of pure hydrogen. As indicated above, the hydrogen to be purified comprises at least water and oxygen as impurities, as well as possibly nitrogen. The zeolitic adsorbent material used in the present invention is a granular material comprising at least one zeolite exchanged and / or impregnated with one or more metals from columns 3 to 12 of the Periodic Table of Elements, in metallic form of zero valence, or in oxidized form or in reduced form. By metal of columns 3 to 12 of the Periodic Table of Elements is meant the transition metals (columns 3 to 11 of the Periodic Table of Elements), including the lanthanides and the actinides, as well as the metals of column 12 of the Periodic Table of Elements, and in particular those chosen from the transition metals (columns 3 to 11 of the Periodic Table of Elements), zinc and cerium, and more preferably from iron, cobalt, cerium, nickel, titanium, copper, zinc, palladium, silver, and platinum, alone or in mixtures of two or more of them. According to a preferred embodiment, the metal is selected from the metals of columns 8 to 12 of the Periodic Table of Elements, and titanium and cerium, alone or in mixtures of two or more of them. In yet another preferred embodiment, the metal is selected from copper, iron and zinc, alone or in mixtures, and optionally with one or more metals selected from palladium, silver and platinum. Of these metals, copper is particularly preferred. Copper / palladium, copper / silver and copper / platinum mixtures are further preferred. Other metals can of course be used, but the preferred metals and metal mixtures listed above have proven to be particularly effective and advantageous in terms of their efficiency / cost of supply ratio. The zeolite adsorbent material usable in the process of the invention therefore comprises at least one zeolite adsorbent material and at least one metal, as set out above. Said at least one metal may be present in said zeolite adsorbent material in native form (or in metallic form, i.e. of zero valence, equal to 0) or oxidized form, or in reduced form, adsorbed totally or at least partially on said at least one zeolite. The metal may also be present in ionic form in the zeolite adsorbent material, and in this case it contributes totally or at least in part to the electronic neutrality of said zeolite adsorbent material. The zeolitic adsorbent material usable in the process of the invention comprises thus at least one metal, as just defined, said at least one metal being able to be deposited and / or impregnated and / or included by ion exchange in the structure of the Zeolite, as explained below. The total mass quantity of metal is generally and most often between 0.1% and 9% by mass, preferably between 0.5% and 8% by mass, more preferably between 1% and 6% by mass, limits included, relative to the total weight of the zeolitic adsorbent material used in the process of the present invention. This mass content is measured by FluoX analysis, as indicated later in the description. According to a preferred embodiment, in the case where the metal or metals are at least partially or totally deposited or impregnated on the zeolite crystals, the particle size of the metal particles is between 1 nm and 250 nm, preferably 5 nm and 250 nm, more preferably between 5 nm and 100 nm, more preferably between 5 nm and 50 nm, for example approximately 15 nm to 20 nm. This particle size is measured by observation with a scanning electron microscope (SEM) equipped with a STEM detector (Scanning Transmission Electron Microscopy). As indicated above, among the preferred metals, it is preferred to use copper and in this case the copper content in the zeolitic adsorbent material used in the process of the present invention is preferably, and most often, between 0.1% and 9% by mass, preferably between 0.5% and 8% by mass, more preferably between 1% and 6% by mass, limits included, relative to the total weight of said zeolitic adsorbent material. This content is in particular much lower than that encountered in zeolitic adsorbent materials containing copper, also called copper-doped zeolitic adsorbents, and known from the prior art. According to a preferred embodiment, the method of the invention is implemented with a zeolitic adsorbent material containing copper and at least one other metal, and preferably at least one other metal chosen from palladium (Pd), platinum (Pt), iron (Fe), zinc (Zn), and mixtures thereof in all proportions. The content of at least one other metal is generally lower than the copper content, and for example of the order of 20% by mass relative to the copper content by mass, preferably of the order of 10% by mass relative to the copper content by mass, and more generally between 0.1% and 20%, most often between 0.1% and 10% by mass relative to the copper content by mass. Said at least one zeolite present in the zeolitic adsorbent material usable in the process of the present invention may be of any type well known to those skilled in the art and may be natural, artificial (modified natural zeolite) or synthetic (obtained by synthesis). Preferably, said at least one zeolite is chosen from LTA, FAU, RHO, MFI zeolites as well as mixtures of two or several of them, Particularly preferred are zeolites chosen from FAU type zeolites, MFI type zeolites, and their mixtures in all proportions and at all Si / Al ratios. It is advantageous to refer to the work "Atlas of Zeolite Framework Types", Elsevier, 5th edition, (2001), for information on the different types of zeolite listed above. It should be understood that the zeolite adsorbent material usable in the process of the present invention may comprise one or more zeolite(s) of identical or different type(s), for example a type X zeolite alone or with an MFI type zeolite, or a type X zeolite with an Si / Al ratio of approximately 1.25, and a type X zeolite with an Si / Al ratio of approximately 1, or a type Y zeolite alone or with an MFI type zeolite, to cite only simple illustrative examples and without any intention of limiting the scope of the present invention. It would therefore not be departing from the scope of the invention if the zeolite consisted of a mixture of structures with different Si / Al molar ratios. According to one embodiment of the invention, the Si / Al ratio of the zeolite or the apparent overall ratio of the mixture of zeolites, if there are several in the agglomerated zeolitic material, can take any value between 1 and 100. According to a preferred aspect, this Si / Al ratio is between 1 and 80, more preferably between 1 and 50, advantageously between 1 and 20. The zeolite adsorbent material usable in the process of the present invention may also comprise the hierarchical porosity homologues of the zeolites listed above. The hierarchical porosity zeolites are well known to those skilled in the art and may, for example, be prepared according to the procedures described in applications WO2015019013 and WO2015028740, or else prepared by chemical, physical or physicochemical post-treatment of traditional zeolites, which are not hierarchical porosity zeolites, also called non-mesoporous zeolites. According to a preferred aspect, the zeolitic adsorbent material of the invention is in the form of an agglomerate, that is to say a material where the zeolite crystals are agglomerated using an agglomeration binder, as is now perfectly known to those skilled in the art. The agglomeration binder can be of any type, but for the purposes of the present invention, an agglomeration binder chosen from clays, aluminas, silicates, and mixtures of two or more of them in all proportions is preferred, and preferably the agglomeration binder is chosen from clays, and more preferably from kaolinic clays, such as kaolin, dickite, halloysite, kaolinite, nacrite, and others. The binder rate, i.e. the mass quantity of agglomeration binder relative to the total weight of the zeolite adsorbent material, is within the ranges known to those skilled in the art, and is generally between 0.1% and 30%, preferably between 1% and 30%, more preferably between 5% and 30%, and advantageously between 10% and 30% by weight. When agglomerating zeolite crystals with at least one agglomeration binder, it may also be advantageous or even desirable to add one or more additives or fillers well known to those skilled in the art, among which may be mentioned, by way of illustrative and non-limiting examples, additives well known to those skilled in the art, and in particular those chosen from shaping aid additives, pore-forming agents, silica, carboxymethylcellulose, and others and mixtures of them or several of them in all proportions to cite only the main additives commonly used during the agglomeration of zeolite crystals with an agglomeration binder. When the binder is a zeolitizable binder, such as for example kaolin, kaolinite, and others, it can be zeolitized in whole or in part, that is to say transformed into Zeolite, generally and most often under the action of a base, such as for example a sodium hydroxide solution, as is well known to those skilled in the art. The zeolitic adsorbent materials suitable for use in the process of the present invention are generally and most often in the form of beads but can take any other form, for example needles, cylinders, hollow cylinders, discs, trilobes, quadrilobes, extruded, crushed and others. The zeolite adsorbent material can be of any size and dimension, however, it is preferred and most often a zeolite adsorbent material whose volume average diameter is between 0.1 mm and 10 mm, preferably between 0.1 mm and 5 mm, more preferably between 0.5 mm and 5 mm, advantageously between 1 mm and 5 mm. The zeolitic adsorbent material suitable for use in the process of the invention is commercially available or can be obtained according to conventional techniques well known to those skilled in the art, from operating methods known in the literature or the internet or even techniques easily adaptable from said known operating methods. In one embodiment, the zeolitic adsorbent material can be easily prepared from zeolitic adsorbents, based on conventional zeolite(s) and / or based on zeolite(s) with hierarchical porosity, and comprising one or more alkali and / or alkaline-earth cations, in particular lithium, sodium, potassium, calcium, strontium, barium, and an agglomeration binder which is optionally zeolitized in whole or at least in part, said zeolitic adsorbent being subjected to an impregnation and / or ion exchange treatment of at least one metal as defined above. previously, generally in the form of salt, according to conventional techniques well known to those skilled in the art. Alternatively, the step of impregnation and / or ion exchange of at least one metal as defined previously can be carried out directly on the zeolite crystals before agglomeration with a binder and shaping. According to a preferred aspect, the process for preparing the zeolitic adsorbent material which can be used in the context of the present invention comprises at least the following steps: a) one or more cationic exchange(s) and / or impregnation(s) of Zeolite crystals with one or more saline solutions of at least one metal chosen from the metals in columns 8 to 12 of the Periodic Table of Elements, as defined above, (b) agglomeration with at least one agglomeration binder, c) heat treatment for hardening (calcination) of said agglomeration binder(s), d) possible at least partial zeolitization of said agglomeration binder(s), and e) recovery and possible activation, generally between 100°C and 550°C, of ​​said zeolitic adsorbent material usable in the context of the present invention. In the method described above, step a) may be carried out one or more times before step b) and / or after step c) and / or d). Generally, without this being obligatory, a cooking step is carried out, preferably between step b) and step d), at a temperature generally between 400°C and 600°C. Alternatively, and when a cooking step is carried out, it may be possible to carry out step a) after this cooking step, and before step d), whether or not a step a) has already been carried out before step b). According to a preferred embodiment of the process for preparing the zeolitic adsorbent material usable in the process of the present invention, a step of shaping said agglomerated material is carried out, according to any method well known to those skilled in the art. This shaping step is carried out after step b) of agglomeration and may be followed by one or more step(s) a) of cation exchange(s) and / or impregnation(s). The heat treatment steps described in the above process must not result in significant sintering of the metal atoms, which must remain as dispersed as possible in the zeolite(s). This point can easily be observed by scanning electron microscopy (SEM) or transmission electron microscopy (TEM). Sintering of the metal atoms is particularly easily avoided, and as is well known, by careful and rigorous control of the temperatures. temperatures and durations of heat treatments. Such methods for preparing zeolitic adsorbent materials exchanged and / or impregnated with / by one or more metals are well known to those skilled in the art, and reference may be made, for example and in a non-limiting manner, to document EP1125635 for a precise description of how to prepare the zeolitic adsorbent materials that can be used in the context of the method of the invention. According to a preferred embodiment, the zeolitic adsorbent material used in the present invention is a granular material comprising at least one zeolite exchanged or impregnated with copper, and optionally one or more other metals in metallic form of zero valence, or in oxidized form or in reduced form chosen from those of columns 3 to 12. A particularly preferred embodiment of the method of the invention uses a zeolitic adsorbent material which is a granular material comprising at least one zeolite exchanged or impregnated with copper, or with copper in a mixture or alloy with one or more metals chosen from palladium, platinum, iron and zinc. According to a further preferred embodiment, the method of the invention uses a zeolitic adsorbent material which is a granular material comprising at least one Faujasite (FAU) type zeolite, preferably a FAU type zeolite with a Si / Al ratio of between 1 and 100, for example a FAU-X type zeolite or a FAU-Y type zeolite, comprising sodium, and further comprising copper, or copper in a mixture or alloy with one or more metals chosen from palladium, platinum, iron and zinc, the metal(s) being able to be exchanged or impregnated in said zeolitic adsorbent material. According to yet another preferred embodiment, the method of the invention uses a zeolitic adsorbent material which is a granular material comprising at least one MFI type zeolite, preferably an MFI type zeolite with a Si / Al ratio of between 10 and 100, comprising sodium, and further comprising copper, or copper in a mixture or alloy with one or more metals chosen from palladium, platinum, iron and zinc, the metal(s) being able to be exchanged or impregnated in said zeolitic adsorbent material. As indicated above, the present invention relates to the method for purifying a hydrogen stream, in particular an electrolytic hydrogen stream, containing, as impurities to be removed, oxygen and water, and possibly nitrogen and possibly other impurities inherent in the hydrogen synthesis process, in particular an electrolytic hydrogen synthesis process. The purification process of the present invention may be carried out according to any method well known to those skilled in the art of gas purification, and more speci- fically by adsorption of impurities on a zeolitic adsorbent material as defined above. Thus, the adsorption process according to the present invention can be chosen from processes of the pressure and / or temperature modulated type, typically from PSA (Pressure Swing Adsorption), PVSA (Pressure Vacuum Swing Adsorption), TSA (Temperature Swing Adsorption), PTSA (Pressure Temperature Swing Adsorption), PVTSA (Pressure Vacuum Temperature Swing Adsorption), and PVTSA (Pressure Vacuum Temperature Swing Adsorption). The fluid to be purified (hydrogen to be purified) contains mainly hydrogen, as previously mentioned, as well as water, oxygen and possibly nitrogen. The water content is generally between 200 ppmv and 1.5 mol%. The oxygen content in the stream is generally between 5 ppmv and 1 mol%. The nitrogen content is between 0 and 1 mol%, generally between 10 ppmv and 1 mol%. The method according to the present invention can be implemented according to any conventional gas separation method, and for example by passage through one or more columns (also called "adsorber(s)") comprising at least one bed of zeolitic adsorbent material as just defined. According to one embodiment, the method of the invention is implemented with at least two adsorbers, in particular when working in continuous flow, according to techniques well known to those skilled in the art. Thus, the fluid to be purified is brought into contact with the zeolitic adsorbent material at a pressure generally between 0.5 MPa and 5 MPa, preferably between 0.9 MPa and 5 MPa, more preferably between 1.5 MPa and 5 MPa, and at a temperature between 10°C and 100°C, preferably between 15°C and 90°C, advantageously between 20°C and 60°C, typically between 25°C and 55°C. In a preferred embodiment, after the adsorption phase, the bed of zeolitic adsorbent material is regenerated, i.e. desorbed either by reducing the pressure and countercurrent evacuation (PSA and VPSA processes), or by reducing the temperature (TSA process), possibly associated with reducing the pressure and countercurrent evacuation (PVTSA process). In the case of PSA and VPSA processes, the desorption pressure is generally between 0.1 MPa and 1 MPa on the one hand and 500 Pa and 95 kPa respectively. As a general rule, and for obvious reasons of ease of implementation of the process and energy savings, the desorption temperature is close to the temperature adsorption, in other words, there is generally no intentional modification of the temperature. According to a further preferred embodiment of the invention, a purge phase can be implemented at the end of the desorption phase, typically by countercurrent reintroduction of a fraction of the purified gas, typically less than 20% of the flow rate produced by an adsorber. It should also be understood that the process of the present invention may also comprise one or more pressure equalization phases between the possible different adsorbers. The pressure equalization phase(s) may advantageously be carried out between the adsorption and desorption phases, according to techniques also well known to those skilled in the art. The advantage of providing one or more pressure equalization phases is in particular to minimize hydrogen losses as much as possible throughout the process. According to yet another variant, it can also be considered to recycle the gas collected at desorption, as is customary to do with hydrogen PSAs. In the case of the TSA and PVTSA processes, a fraction of the purified gas (typically less than 20% of the flow produced by the adsorber) is heated to a temperature between 40°C and 250°C, then injected counter-currently onto the adsorber, possibly at a reduced pressure compared to the adsorption phase (PVTSA), i.e. between | kPa and 3 MPa. As for PSA and VPSA, different pressure equalization and purge configurations can be considered. In the process of the present invention, the adsorption and desorption phases follow one another cyclically. The process may also comprise a step of drying the gas flow, before and / or after passing over the zeolitic adsorbent material comprising at least one metal according to the invention. Being able to dry, i.e. adsorb the water present or formed on the same material, will simplify the processes downstream of the electrolysers while producing hydrogen of the required quality. The DEOXO unit will no longer be necessary thanks to the implementation of the process of the invention. The method of the invention thus has numerous advantages, and in particular that of being able to both reduce the dissolved oxygen in the hydrogen stream and adsorb the water possibly already present in the hydrogen stream as well as the water formed by the reduction of the dissolved oxygen. The method of the invention thus makes it possible to easily obtain, on an industrial level, hydrogen streams and in particular electrolytic hydrogen streams, comprising less than 5 ppmv of oxygen, and less than 1 ppmv of water. According to another aspect of the invention, it relates to a flow of purified hydrogen obtained according to the method described above, and its use as fuel, as an industrial reagent, in the electrical and electronic fields, and in particular in fuel cells, but also to supply organic hydrogen carrier (LOHC) cycles, such as toluene (methylcyclohexane) or other aromatic hydrocarbons, such as benzyltoluene or dibenzyltoluene (see for example international applications WO2014082801 and WO2021176170), to name just a few known applications, and more generally for syntheses in the chemical, pharmaceutical and petrochemical industries. According to another aspect, the invention relates to the use of the zeolitic adsorbent material as defined above for the purification of a hydrogen stream, and in particular for the purification of electrolytic hydrogen. According to yet another aspect, the invention relates to a process for preparing high purity hydrogen comprising at least the following steps: 1) electrolysis of an aqueous solution comprising mainly hydrogen oxide to generate a flow of hydrogen and a flow of oxygen, 2) recovery of the hydrogen flow from step 1) of electrolysis, 3) purification of the hydrogen stream recovered in step 2) by passage over a zeolitic adsorbent material, as defined previously, and 4) recovery of high purity hydrogen. It should be understood that the process for preparing high-purity hydrogen according to the invention comprises a step 1) of electrolysis which can be carried out in a conventional manner well known to those skilled in the art. This process thus makes it possible to obtain very high purity hydrogen efficiently and economically, and in particular more economically than the synthesis processes known today for preparing hydrogen by electrolysis of water. Analytical techniques Si / Al molar ratio and exchange rate The measurement of the Si / Al molar ratio and the exchange rate is carried out by any analytical chemical analysis techniques known to those skilled in the art. Among these techniques, we can cite the chemical analysis technique by X-ray fluorescence as described in the standard NF EN ISO 12677: 2011 on a wavelength dispersive spectrometer (WDXRF), for example Tiger S8 from the Bruker company. X-ray fluorescence is a spectral technique that exploits the photoluminescence of atoms in the X-ray range to establish the elemental composition of a sample. The excitation of atoms, generally by an X-ray beam or by bombardment with electrons, generates specific radiation after returning to the ground state of the atom. The X-ray fluorescence spectrum has the advantage of depending very little on the chemical combination of the element, which offers a determination precise, both quantitative and qualitative, We obtain in a conventional manner after calibration for each oxide a measurement uncertainty of less than 0.4% by weight. These elementary chemical analyses make it possible to verify the Si / Al molar ratio of the starting zeolite, the content of deposited metal(s) and to verify the quality of the ion exchange. In the description of the present invention, the measurement uncertainty of the Si / Al molar ratio is + 5%. The quality of the ion exchange is linked to the number of moles of sodium oxide, NayO, remaining in the agglomerated zeolite adsorbent after exchange. It should be noted that the contents of different oxides are given as a percentage by weight relative to the total weight of anhydrous zeolite adsorbent material. The Si / Al molar ratio of the zeolite present in the zeolitic adsorbent material is measured by solid-state Nuclear Magnetic Resonance (NMR) spectroscopy of silicon. In the description of the present invention, the measurement uncertainty of the Si / Al molar ratio is + 5%. Granulometry of metal particles The estimation of the number-average diameter of the metal particles contained in the zeolite adsorbent material is carried out by observation under a scanning electron microscope (SEM). To estimate the size of metal particles in the samples, a set of images is taken at a magnification of at least 5000. The diameter of at least 200 particles is then measured using dedicated software, for example Smile View software from the publisher LoGraMi. The accuracy is around 3%. The measurement of the histogram formed from the said diameter measurements simultaneously allows the determination of the standard deviation o of its distribution. Particle size of zeolite adsorbents: The determination of the volume average diameter of zeolite adsorbents is carried out by analyzing the particle size distribution of an agglomerate sample by imaging according to ISO 13322-2:2006, using a conveyor belt allowing the sample to pass in front of the camera lens. The volume mean diameter is then calculated from the particle size distribution by applying the ISO 9276-2:2001 standard. In this document, the term "volume mean diameter" or "size" is used for zeolite agglomerates. The accuracy is of the order of 0.01 mm for the agglomerate size range of the invention. Qualitative analysis by X-ray diffraction The purity of zeolites in zeolitic adsorbent materials is assessed by X-ray diffraction analysis, known to those skilled in the art by the acronym DRX. This identification is carried out on a Bruker brand DRX device. This analysis makes it possible to identify the different zeolites present in the adsorbent material since each zeolite structure has a unique diffractogram defined by the positioning of the diffraction peaks and by their relative intensities. Prior to measurement, the zeolite materials are crushed then spread and smoothed on a sample holder by simple mechanical compression. The conditions for acquiring the diffractogram produced on the Bruker D5000 device are as follows: * Cu tube used at 40 kV — 30 mA: * slit size (diverging, diffusion and analysis) = 0.6 mm; * filter: Ni; * rotating sample device: 15 rpm”! ; * measuring range: 3° < 20 < 50°; “step: 0.02°; * counting time per step: 2 seconds. The interpretation of the diffractogram obtained is carried out with EVA software with identification of zeolites using the ICDD PDF-2 base, release 2011. Microcrystallinity by volume of Dubinin The volume of Dubinin (or microporous Vni) is determined in a conventional manner well known to those skilled in the art, in particular from the measurement of the adsorption isotherm of a gas at its liquefaction temperature, for example nitrogen, argon, oxygen, and others. Preferably, nitrogen is used. Prior to this adsorption measurement, the zeolite crystals of the invention are degassed between 300°C and 450°C for a period ranging from 9 hours to 16 hours, under vacuum (Pressure < 6.7.10- Pa). For example, for a zeolite with FAU or MFI structure, the measurement of the nitrogen adsorption isotherm at 77K is then carried out on a Micromeritics ASAP 2020 type device, taking at least 35 measurement points at relative pressures with a P / PO ratio between 0.002 and 1. The micropore volume is determined according to the Dubinin and Raduskevitch equation from the isotherm obtained, applying the ISO 15901-3:2007 standard.The micropore volume thus evaluated is expressed in cm* of liquid adsorbent per gram of anhydrous adsorbent. The measurement uncertainty is + 0.003 cm* g".

Claims

Claims

1. A method of purifying a hydrogen stream containing water, oxygen and possibly nitrogen, including: - at least one step of bringing the hydrogen flow to be purified into contact with a zeolitic adsorbent material comprising at least one metal from columns 3 to 12 of the Periodic Table of Elements, in the form metallic of zero valence, or in oxidized form or in form reduced, and - at least one step of recovering purified hydrogen stream.

2. Method according to claim 1, in which the hydrogen to be purified includes electrolytic hydrogen.

3. A method according to claim | or claim 2, wherein the hydrogen to be purified comprises from 60 mol% to 99.99 mol% of pure hydrogen, preferably from 80 mol% to 99.99 mol% of pure hydrogen, more preferably from 90 mol% to 99.99% molars of pure hydrogen and more preferably 95% molars at 99.99 mol% pure hydrogen, typically 96.50 mol% to 99.99 mol% pure hydrogen, and includes at least water and oxygen as impurities, as well as optionally nitrogen.

4. A method according to any one of the preceding claims, in which said at least one metal is chosen from iron, cobalt, cerium, nickel, titanium, copper, zinc, palladium, silver, and platinum, alone or in mixtures of two or more of them.

5. A method according to any one of the preceding claims, in which the zeolitic adsorbent material comprises at least one Zeolite chosen from LTA, FAU, RHO, MFI zeolites as well as mixtures of two or more of them, and preferably chosen among FAU type zeolites, MFI type zeolites, and their mixtures in all proportions and at all Si / Al ratios.

6. A method according to any preceding claim, in in which the zeolite adsorbent material is a granular material comprising at least one zeolite exchanged or impregnated with copper, and possibly one or more other metals in me- metal of zero valence, or in oxidized form or in reduced form chosen from those in columns 3 to 12.

7. A method according to any preceding claim, in in which the flow of hydrogen to be purified is brought into contact with the material zeolite adsorbent at a pressure between 0.5 MPa and 5 MPa, preferably between 0.9 MPa and 5 MPa, more preferably between 1.5 MPa and 5 MPa, and at a temperature between 10°C and 100°C, preferably between 15°C and 90°C, advantageously between 20°C and 60°C, typically between 25°C and 55°C.

8. Use of a zeolitic adsorbent material comprising at least one metal chosen from among the metals in columns 3 to 12 of the Periodic Table elements, including the lanthanides and actinides, and preferably chosen from iron, cobalt, cerium, nickel, titanium, copper, zinc, palladium, silver, and platinum, alone or in mixtures of two or more of them, for the purification of a hydrogen stream, and in particular for the purification of electrolytic hydrogen.

9. Use of a purified hydrogen stream obtained according to the process of any one of claims | to 7, as fuel, as industrial reagent, in the electrical and electronic fields, in fuel cells, to power the cycles of or- hydrogen ganics (LOHC), and for syntheses in industry chemical, pharmaceutical and petrochemical.

10. A process for preparing high purity hydrogen comprising at minus the following steps: 1) electrolysis of an aqueous solution comprising mainly hydrogen oxide to generate a hydrogen stream and a stream of oxygen, 2) recovery of the hydrogen flow from step 1) of electrolysis, 3) purification of the hydrogen stream recovered in step 2) according to the method of any one of claims 1 to 7, and 4) recovery of high purity hydrogen.