ELECTROLYTIC OXYGEN PURIFICATION

Abstract

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

Description

Description Title of the invention: ELECTRICAL OXYGEN PURIFICATION TROLYTIC

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

[0002] — The problem of oxygen purification is becoming a challenge today important. Indeed, while until now hydrogen has been obtained in large quantities by Steam reforming, current environmental constraints linked to global warming Climate change has prompted scientists to reconsider water electrolysis for to produce hydrogen.

[0003] — In this electrolysis process, a water molecule is separated to give one mole of hydrogen and half a mole of oxygen, according to the chemical equation H,0 H, + 1 / 2 O,. The electrolysis of water therefore generates a significant amount of oxygen which it It must be purified in order to be usable. Indeed, the oxygen produced by electrolysis of Water is often polluted by hydrogen co-produced by the process, particularly due to excessive permeation of hydrogen through the separating membrane(s) or of the solubilization of hydrogen in the electrolyte. As for the water present in the oxygen flow, this generally comes from gaseous entrainments, while Nitrogen, for example, comes from the inerting phases at the start-up of the electrolyzer and from its solubilization in cold water, often under pressure, introduced into the electrolyzer. The contaminants to be removed from the oxygen stream are therefore hydrogen, nitrogen, water and possibly traces of electrolyte, for example KOH type.

[0004] Indeed, certain industrial applications and processes require oxygen, the as pure as possible, with the highest possible purity, for example greater than 99%, in order to optimize the efficiency of said oxygen in these processes or applications.

[0005] The prior art already provides numerous solutions for eliminating, in particular the hydrogen contained in a gas. For example, document EP0089183 describes a process for removing hydrogen from a gas that may also contain oxygen. This process involves bringing said gas into contact with ambient temperature with a catalyst comprising a tin and alumina oxide support impregnated with 0.25% to 2.5% by weight of platinum and 0.25% to 2.5% by weight of palladium. The operation is carried out at room temperature. Hydrogen is oxidized to water but Water is not removed. Inlet hydrogen levels vary between 0.2% and 2% and The hydrogen content at the outlet varies between 0.04% and 0.09%. Y. Jang et al. (“Effect of a modified 13X zeolite support in Pd-Based catalysts for hydrogen oxidation at room temperature”, RSC Adv, 11, (2021), 38047-38053) investigated the effect of a modified, palladium-doped 13X zeolite on the oxidation of hydrogen to water. Specifically, the authors demonstrated that when a 13X zeolite underwent acid treatment followed by specific calcination, the activity of the catalysts was significantly increased. In this article, the zeolite is treated with an acid, which leads to degradation of the crystal structure. Therefore, it is not a zeolite that is involved in the oxidation of hydrogen to water. The work of O. Yu. Golubeva et al. (“Catalytic hydrogen oxidation using zeolite RHO modified by silver nanoparticles”, Glass Physics and Chemistry, 3&(5), (2012), 455-459) describe the catalytic activity of RHO zeolite modified by silver ions.It has been demonstrated that the incorporation of a large quantity of silver (greater than 17%, expressed as Ag2O) into the RHO structure allows the oxidation of hydrogen in air (mostly nitrogen). This reaction is carried out at high temperature (around 200°C). However, no indication of the presence or removal of water is given. Prior art currently offers no acceptable solution. While it might be conceivable that nitrogen and water could be easily removed by passing through a CaX-type sieve and a 4A-type sieve, respectively, separating hydrogen would be more difficult because this gas does not adsorb onto the sieves. Therefore, there is currently no acceptable industrial solution for purifying a gas stream containing oxygen contaminated with hydrogen, water, nitrogen, and possibly traces of residual electrolytes. There remains a need for an oxygen purification process that is easily industrializable, less expensive, and simple to implement, particularly a hydrogen purification process that is less expensive and easier to implement than those using currently available techniques. Thus, one of the objectives of the present invention is to provide an oxygen purification process that overcomes the drawbacks encountered in the prior art, and in particular, to purify oxygen more easily, specifically by removing both hydrogen and water present as impurities in an oxygen stream. Another objective of the present invention is to provide a method for purifying oxygen to remove both hydrogen and water present as impurities in an oxygen stream, as well as nitrogen and other impurities such as traces of residual electrolytes, such as potassium hydroxide, particularly for oxygen streams from an electrolyzer, also known as electrolytic oxygen. Further objectives will become apparent in the in light of the description of the present invention which follows. The Applicant has now discovered that it is possible to meet, in whole or at least in part, the objectives set out above and in particular to purify an oxygen stream, in particular an electrolytic oxygen stream, by eliminating, or at least greatly reducing, the levels of hydrogen and water, as well as where appropriate the levels of nitrogen and other traces of residual electrolytes, in a simple, efficient and relatively inexpensive manner, and in particular by overcoming in whole or in part the problems encountered in the prior art. The present invention thus proposes an “all-in-one” process for purifying and drying oxygen, by removing hydrogen and water using a single zeolite adsorbent material, the zeolite of which has undergone at least one partial cation exchange and / or impregnation with at least one transition metal. More specifically, the present invention relates to a method for purifying an oxygen stream containing water, hydrogen, and optionally nitrogen, comprising: - at least one step of contacting the oxygen stream to be purified with a zeolitic adsorbent material comprising at least one metal, in a zero-valence metallic form, or in an oxidized or reduced form, and - at least one step for recovering purified oxygen flow. In one embodiment of the invention, the oxygen to be purified comprises electrolytic oxygen, that is, oxygen obtained by the electrolysis of water. In a preferred embodiment, the oxygen to be purified comprises predominantly oxygen, that is, from 60% to 99.99% pure oxygen, preferably from 80% to 99.99% pure oxygen, more preferably from 90% to 99.99% pure oxygen, and more preferably from 95% to 99.99% pure oxygen, typically from 96.50% to 99.99% pure oxygen. As stated above, the oxygen to be purified comprises at least water and hydrogen as impurities, and optionally 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 in metallic form of zero valence, or in oxidized form or in reduced form. The term "metal" refers to the metals of the Periodic Table of Elements, and in particular the metals of columns 3 to 15 of the Periodic Table of Elements, excluding metalloids and nonmetals. Preferably, the term "metal" refers to the metals of columns 3 to 14 of the Periodic Table of Elements, excluding metalloids and nonmetals, and preferably again, "metal" We mean metals chosen from palladium, platinum, silver, titanium, tin, zinc, nickel, cobalt, iron and copper, alone or in mixtures of two or more of them. Preferably, the metal is a metal selected from palladium (Pd), platinum (Pt), copper (Cu), iron (Fe), nickel (Ni), zinc (Zn), tin (Sn), cobalt (Co), and mixtures of two or more of these, in any proportions, and most preferably from palladium (Pd), platinum (Pt), copper (Cu), nickel (Ni), tin (Sn), iron (Fe), and mixtures of two or more of these, in any proportions. Examples of metal mixtures, by way of non-limiting explanation, include mixtures (or alloys) of Pd / Ni, Pt / Ni, Pd / Pt / Ni, Sn / Pd, Sn / Pt, Sn / Pd / Pt, and Cu / Ag. 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 / supply cost 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 described above. This at least one metal may be present in the zeolite adsorbent material in its native form (or metallic form, i.e., with a valence of zero, equal to 0) or in an oxidized form, or in a reduced form, adsorbed totally or at least partially onto the at least one zeolite. The metal may also be present in ionic form in the zeolite adsorbent material, and in this case, it contributes in whole or at least in part to the electronic neutrality of the zeolite adsorbent material. The zeolite adsorbent material usable in the process of the invention thus comprises 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 later. The total mass content of metal is generally and most often between 0.1% and 7% by mass, preferably between 0.5% and 6% by mass, and even more preferably between 1% and 5% by mass, inclusive, relative to the total weight of the zeolite adsorbent material used in the process of the present invention. This mass content is measured by FluoX analysis, as described later. According to a preferred embodiment, where the metal or metals are at least partially or totally deposited or impregnated onto the zeolite crystals, the particle size of the metallic particles is between 1 nm and 250 nm, preferably between 5 nm and 250 nm, preferably still between 5 nm and 100 nm, even better between 5 nm and 50 nm, for example about 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 previously stated, among the preferred metals, copper is preferred, and in this case, the copper content in the zeolite adsorbent material used in the process of the present invention is preferably, and most often, between 0.1% and 7% by mass, preferably between 0.5% and 6% by mass, and preferably again between 1% and 5% by mass, inclusive, relative to the total weight of said zeolite adsorbent material. This content is notably much lower than that found in copper-containing zeolite adsorbent materials, also called copper-doped zeolite adsorbents, which are known in the prior art. According to a preferred embodiment, the process of the invention is carried out with a zeolite adsorbent material containing copper and at least one other metal, preferably at least one other metal chosen from zinc (Zn) and silver (Ag), to mention only the most common mixtures, but also from palladium (Pd), platinum (Pt), iron (Fe), and mixtures thereof in all proportions. The content of at least one other metal is generally lower than the copper content, and for example, on the order of 20% by mass relative to the copper content, preferably on the order of 10% by mass relative to the copper content, and more generally between 0.1% and 20%, most often between 0.1% and 10% by mass relative to the copper content. The at least one zeolite present in the zeolite 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 selected from LTA, FAU, RHO, and MFI zeolites, as well as mixtures of two or more of them. Zeolites selected from FAU-type zeolites, MFI-type zeolites, and their mixtures in all proportions and at all Si / Al ratios are particularly preferred. Reference may be made to the publication "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 zeolites of the same or different types, for example, a zeolite selected from type X, type Y, or type MFI zeolites, alone or in mixtures, for example, zeolite X alone or with a type MFI zeolite, or for example, zeolite Y alone or with a type MFI zeolite, or a type MFI zeolite alone, or for example, zeolite X mixed with zeolite Y, or for example, a mixture of type MFI zeolite with zeolite X and zeolite Y, to name only a few. These are simple illustrative examples and are given without any intention of limiting the scope of the present invention. Therefore, it would not depart from the scope of the invention if the zeolitic adsorbent material were composed of a mixture of structures with different Si / Al molar ratios. According to one embodiment of the invention, the Si / AI ratio of the zeolite, or the overall apparent ratio of the mixture of zeolites, if there are several in the agglomerated zeolite material, can take any value between 1 and 100. According to a preferred aspect, this Si / AI ratio is between 1 and 80, preferably between 1 and 50, advantageously between 1 and 20. The zeolite adsorbent material usable in the process of the present invention may also include hierarchically porosity counterparts of the zeolites listed above. Hierarchically porosity zeolites are well known to those skilled in the art and can, for example, be prepared according to the procedures described in applications WO2015019013 and WO2015028740, or prepared by chemical, physical or physico-chemical post-treatment of traditional zeolites, which are not hierarchically porosity zeolites, also called non-mesoporous zeolites. According to a preferred aspect, the zeolite adsorbent material of the invention is in the form of an agglomerate, that is to say, a material in which the zeolite crystal(s) are agglomerated using an agglomerating binder, as is now perfectly known to those skilled in the art. The agglomerating binder can be of any type, but for the purposes of the present invention, an agglomerating binder chosen from clays, aluminas, silicates, and mixtures of two or more of them in any proportions is preferred, and preferably the agglomerating binder is chosen from clays, and even more preferably from kaolinitic clays, such as kaolin, dickite, halloysite, kaolinite, nacrite, and others. The binder content, that is, the mass quantity of agglomeration binder relative to the total weight of the zeolitic 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%, preferably still between 5% and 30%, and advantageously between 10% and 30% by weight. During the agglomeration of zeolite crystal(s) 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, by way of illustration and not limitation, may be cited the additives well known to those skilled in the art, and in particular those chosen from among the shaping aids, porogenic agents, silica, carboxymethylcellulose, and others, and mixtures of them or several of them in any proportion, to name only the main additives commonly used when agglomerating zeolite crystals with an agglomeration binder. When the binder is a zeolithizable binder, such as kaolin, kaolinite, and others, it can be zeolithized in whole or in part, that is to say, transformed into Zeolite, generally and most often under the action of a base, such as a sodium hydroxide solution, as is well known to those skilled in the art. 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. Zeolitic adsorbent material can be of all sizes and dimensions, however, a zeolitic adsorbent material with an average volume diameter of between 0.1 mm and 10 mm is preferred most often, preferably between 0.1 mm and 5 mm, preferably even 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 using conventional techniques well known to those skilled in the art, from methods known in the literature or the internet, or from techniques easily adaptable from said known methods. In one embodiment, the zeolitic adsorbent material can be easily prepared from zeolitic adsorbents, based on conventional zeolite(s) and / or 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 possibly zeolithized 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, generally in the form of a salt, according to classic techniques well known to those skilled in the art. Alternatively, the impregnation and / or ion exchange step of at least one metal as defined above 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 usable within the scope of the present invention comprises at least the following steps: a) one or more cation exchange(s) and / or impregnation(s) of Zeolite crystals with one or more saline solutions of at least one metal chosen from the metals from columns 8 to 15 of the Periodic Table of Elements, excluding non-metals and metalloids, as defined previously, b) agglomeration with at least one agglomeration binder, c) heat treatment for hardening (calcination) of said agglomeration binder(s), d) possible zeolithization, at least partial, of said binder(s) of urban areas, and e) recovery and possible activation, generally between 100°C and 550°C, of ​​said zeolitic adsorbent material usable within the framework of the present invention. In the process described above, step a) can be carried out one or more times before step b) and / or after step c) and / or d). A cooking step is generally carried out, although not mandatory, preferably between step b) and step d), at a temperature generally between 400°C and 600°C. Alternatively, 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 step a) has already been carried out before step b). According to a preferred embodiment of the process for preparing the zeolite adsorbent material usable in the process of the present invention, a shaping step of 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 should remain as dispersed as possible within the zeolite(s). This can easily be observed by scanning electron microscopy (SEM) or transmission electron microscopy (TEM). Sintering of the metal atoms is, in particular, easily avoided, as is well known, by careful and rigorous control of the temperatures and durations of the heat treatments. Such processes for preparing exchanged and / or impregnated zeolitic adsorbent materials with one or more transition metals are well known to those skilled in the art, and reference can be made, for example and without limitation, to document EP1125635 for a precise description of how to prepare zeolitic adsorbent materials usable in the context of the process of the invention. According to a preferred embodiment, the zeolite adsorbent material used in the present invention is a granular material comprising at least one zeolite exchanged or impregnated with one or more metals selected from palladium, platinum, silver, titanium, tin, zinc, nickel, cobalt, iron, and copper under metallic form with zero valence, or in oxidized form or in reduced form. A particularly preferred embodiment of the process of the invention uses a zeolitic adsorbent material which is a granular material comprising at least one zeolite exchanged or impregnated with a metal selected from copper, palladium, platinum, iron and zinc, alone or in mixtures of two or more of them in any proportions. According to yet another preferred embodiment, the process of the invention uses a zeolitic adsorbent material which is a granular material comprising at least one Faujasite type zeolite (FAU), preferably an FAU type zeolite with a Si / Al ratio 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 selected from palladium, platinum, iron and zinc, the transition metal(s) being able to be exchanged or impregnated in said zeolitic adsorbent material. According to yet another preferred embodiment, the process 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 between 10 and 100, comprising sodium, and further comprising copper, or copper in a mixture or alloy with one or more metals selected from palladium, platinum, iron and zinc, the metal or metals being able to be exchanged or impregnated in said zeolitic adsorbent material. According to one embodiment of the invention, the process uses a Zeolitic adsorbent material comprising at least one zeolite selected from FAU type zeolites, MFI type zeolites, and mixtures thereof, and at least one metal, in metallic form of zero valence, or in oxidized form or in reduced form, is selected from copper, palladium, platinum, iron and zinc, and mixtures thereof, the metal or metals being able to be exchanged or impregnated in said zeolitic adsorbent material. As previously stated, the present invention relates to the process of purifying an oxygen stream, in particular an electrolytic oxygen stream, containing, as impurities to be removed, hydrogen and water, and possibly nitrogen and possibly other impurities inherent in the oxygen synthesis process, in particular the electrolytic oxygen synthesis process. The purification process of the present invention can be carried out according to any method well known to those skilled in the art of gas purification, and more specifically by adsorption of impurities onto a zeolite adsorbent material as defined above. Thus, the adsorption process according to the present invention can be chosen from among pressure- and / or temperature-modulated processes, typically from among PSA (Pressure Swing Adsorption) processes. Pressure Modulated), PVSA (“Pressure Vacuum Swing Adsorption”, or Pressure Modulated Adsorption, with the use of sub-atmospheric pressure desorption), TSA (“Temperature Swing Adsorption”, Temperature Modulated Adsorption), PTSA (“Pressure Temperature Swing Adsorption”, or Temperature and Pressure Modulated Adsorption), PVTSA (“Pressure Vacuum Temperature Swing Adsorption”, Temperature and Pressure Modulated Adsorption, with the use of sub-atmospheric pressure desorption). The fluid to be purified contains primarily oxygen, as previously mentioned, as well as water, hydrogen, and possibly nitrogen. The water content is generally between 200 ppmv and 1.5 mol%. The hydrogen content in the stream is generally between 5 ppmv and 1 mol%. The nitrogen content is between 0 and 1 mol%, typically between 10 ppmv and 1 mol%. The process according to the present invention can be implemented using any conventional gas separation method, for example, by passing the gas through one or more columns (also referred to as "adsorber(s)") comprising at least one bed of zeolite adsorbent material as defined above. In one embodiment, the process of the invention is implemented with at least two adsorbers, particularly when operating 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, preferably still 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 counter-current evacuation (PSA and VPSA processes), or by reducing the temperature (TSA process), possibly associated with a reduction in pressure and counter-current 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 on the other. As a rule, and for obvious reasons of ease of process implementation and energy savings, the desorption temperature is close to the adsorption temperature; in other words, no intentional temperature modification is usually made. According to yet another preferred embodiment of the invention, a purging phase can be implemented at the end of the desorption phase, typically by reintroduction to counter-current of a fraction of the purified gas, typically less than 20% of the flow produced by an adsorber. It should also be understood that the process of the present invention may also include one or more pressure equalization phases between the various adsorbents. The pressure equalization phase(s) may advantageously be carried out between the adsorption and desorption phases, using techniques also well known to those skilled in the art. The benefit of including one or more pressure equalization phases is, in particular, to minimize as much as possible the losses of oxygen and hydrogen throughout the entire process. Similarly, it may be possible to recycle the gas collected during desorption, as is common practice with hydrogen-based PSA processes. In the case of 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 pressure reduced relative to the adsorption phase (PVTSA), i.e., between 1 kPa and 3 MPa. As with 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 each other cyclically. The process may also include a step of drying the gas stream, before and / or after passing over the zeolite adsorbent material comprising at least one metal according to the invention. The ability to dry, i.e. adsorb water present or formed on the same material, will simplify processes downstream of electrolyzers while producing a high-purity oxygen flow, particularly of the quality required in many fields of application. The process of the invention thus offers numerous advantages, particularly the ability to simultaneously reduce the hydrogen dissolved in the oxygen stream and adsorb any water already present in the hydrogen stream, as well as the water formed by the reduction of dissolved oxygen. The process of the invention therefore makes it easy to obtain, on an industrial scale, high-purity oxygen streams, and in particular oxygen streams with a purity greater than 99%, and more specifically electrolytic oxygen streams with a purity greater than 99% and containing less than 5 ppmv of hydrogen and less than 1 ppmv of water. According to another aspect of the invention, it relates to a purified oxygen stream obtained according to the process described above, and its use as an industrial product or reagent in various fields, such as, for example, metallurgy or medicine, to name just a few known applications. It should be noted that one of the main advantages is the ability to have oxygen free or almost free of hydrogen, for obvious safety reasons. According to another aspect, the invention relates to the use of the zeolitic adsorbent material as defined above for the purification of an oxygen stream, and in particular for the purification of electrolytic oxygen. According to yet another aspect, the invention relates to a process for preparing high-purity oxygen comprising at least the following steps: 1) Electrolysis of an aqueous solution consisting mainly of hydrogen oxide to generate a flow of hydrogen and a flow of oxygen, 2) recovery of the oxygen flow from step 1) of electrolysis, 3) purification of the oxygen stream recovered in step 2) by passing it through a zeolitic adsorbent material, as defined previously, and 4) recovery of high purity oxygen. It should be understood that the process for preparing high-purity oxygen according to the invention includes a step 1) of electrolysis which can be carried out in a conventional manner and well known to those skilled in the art. This process thus allows for the efficient and economical production of very high-purity oxygen, and in particular, is more economical than currently known methods of oxygen synthesis by water electrolysis. Analytical techniques Si / Al molar ratio and exchange rate The measurement of the Si / Al molar ratio and the exchange rate is carried out using all analytical techniques for chemical analysis known to those skilled in the art. Among these techniques, we can mention the chemical analysis technique by X-ray fluorescence as described in the standard NF EN ISO 12677:2011 on a wavelength dispersive X-ray spectrometer (WDXRF), for example the Tiger S8 from Bruker. X-ray fluorescence is a spectral technique that exploits the photoluminescence of atoms in the X-ray range to determine the elemental composition of a sample. Excitation of atoms, generally by an X-ray beam or by electron bombardment, generates specific radiations after the atom returns to its ground state. The X-ray fluorescence spectrum has the advantage of being largely independent of the element's chemical composition, thus providing a precise determination, both quantitative and qualitative. Typically, after calibration, a measurement uncertainty of less than 0.4% by weight is obtained for each oxide. These elemental chemical analyses allow us to verify the Si / Al molar ratio of the starting zeolite, the content of the deposited metal(s), and the quality of the ion exchange. In the description of the present According to the invention, the measurement uncertainty of the Si / Al molar ratio is +5%. The quality of the ion exchange is related to the number of moles of sodium oxide, Na:O, remaining in the agglomerated zeolite adsorbent after exchange. It should be noted that the contents of the various 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 zeolite 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%. Particle size distribution of metallic particles The estimation of the average number diameter of the metallic particles contained in the zeolitic adsorbent material is carried out by observation using a scanning electron microscope (SEM). To estimate the size of metallic particles in the samples, a series of images are taken at a magnification of at least 5000x. The diameter of at least 200 particles is then measured using dedicated software, such as Smile View from LoGraMi. The accuracy is approximately 3%. The histogram constructed from these diameter measurements simultaneously allows for the determination of the standard deviation θ of its distribution. Particle size distribution of zeolitic adsorbents: The determination of the average volume diameter of zeolitic 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 average volume diameter is then calculated from the particle size distribution by applying ISO 9276-2:2001. In this document, the terms "average volume diameter" or "size" are used for zeolitic agglomerates. The accuracy is on the order of 0.01 mm for the size range of agglomerates 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 XRD. This identification is performed on a Bruker brand XRD instrument. 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 zeolitic materials are crushed, then spread and smoothed. on a sample holder by simple mechanical compression. The acquisition conditions for the diffractogram produced on the Bruker D5000 instrument are as follows: * Cu tube used at 40 kV — 30 mA: * size of the slits (diverging, diffusion and analysis) = 0.6 mm; * filter: Ni; * rotating sample device: 15 rpm”! ; * measurement range: 3° < 20 < 50°; "step: 0.02°; * Counting time per step: 2 seconds. The interpretation of the obtained diffractogram was performed using EVA software, with zeolite identification using the ICDD PDF-2 database, release 2011. Microcrystallinity by Dubinin volume The Dubinin volume (or microporous Vi) is determined using a method conventional and well-known to those skilled in the art, notably by measuring 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 of 9 to 16 hours under vacuum (pressure < 6.7 x 10⁻³ 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 microporous volume is determined according to the Dubinin and Raduskevitch equation from the isotherm obtained, applying the ISO 15901-3:2007 standard.The microporous 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 an oxygen stream containing water, hydrogen and possibly nitrogen, including: - at least one step of bringing the oxygen flow to be purified into contact with a zeolitic adsorbent material comprising at least one metal, in metallic form of zero valence, or in oxidized form or in reduced form, and - at least one step of recovering purified oxygen stream.

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

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

4. A method according to any one of the preceding claims, in wherein said at least one transition metal is chosen from metals from columns 3 to 15 of the Periodic Table of Elements, excluding metalloids and non-metals, preferably among the metals of columns 3 to 14 of the Periodic Table of Elements, excluding metalloids and non-metals, and preferably among the palladium, platinum, silver, titanium, tin, zinc, nickel, cobalt, iron and copper, and alone or in mixtures of two or more of them.

5. A method according to any preceding claim, 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 which the zeolitic adsorbent material comprises at least one Zeolite chosen from FAU type zeolites, MFI type zeolites, and their mixtures and at least one metal, in metallic form of zero valence, or in oxidized form or in reduced form, chosen from copper, palladium, platinum, iron and zinc, and mixtures thereof, the metal(s) which can be exchanged or impregnated in said zeo-adsorbent material lithic.

7. A method according to any preceding claim, in in which the flow of oxygen 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, in metallic form of zero valence, or in oxidized form or in reduced form in which said at least one metal is chosen from metals from columns 3 to 15 of the Periodic Table of Elements, the exclusion of metalloids and non-metals, preferably among the metals from columns 3 to 14 of the Periodic Table of Elements, the exclusion of metalloids and non-metals, and preferably still chosen from palladium, platinum, silver, titanium, tin, zinc, nickel, cobalt, iron and copper, alone or in mixtures of two or several of them, for the purification of an oxygen flow, and in especially for electrolytic oxygen purification.

9. Use of a purified oxygen stream obtained according to the method of one any of claims | to 7, as a product or reactant in- dustriel.

10. A process for preparing high purity oxygen comprising at least 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 oxygen flow from step 1) of electrolysis, 3) purification of the oxygen flow recovered in step 2) by passage over a zeolitic adsorbent material according to the method of any of claims 1 to 7, and 4) high purity oxygen recovery.