Purification of electrolytic oxygen

Abstract

The invention relates to a method for purifying an oxygen stream contaminated by water, hydrogen and possibly nitrogen, said method comprising contacting the oxygen stream to be purified with a zeolite-based adsorbent material comprising at least one metal in the form of a zero-valent metal, or in the oxidized or reduced form, and recovering the purified oxygen stream. The invention also relates to the use of a zeolite-based adsorbent material comprising at least one transition metal for purifying oxygen, and to the use of the oxygen thus purified in industrial processes.

Description

[0001] The present invention relates to a process for purifying oxygen from an electrolyzer, and more particularly to a process for purifying oxygen containing water and hydrogen, and possibly traces of nitrogen and / or traces of residual electrolyte such as potassium hydroxide.

[0002] The purification of oxygen has now become a major issue. In particular, while hydrogen has been obtained so far mostly by steam reforming, the current ecological constraints related to global warming have prompted scientists to reconsider the production of hydrogen by electrolysis of water.

[0003] In this electrolysis process, one mole of water molecule is dissociated to produce one mole of hydrogen and half a mole of oxygen according to the chemical equation H2O -> H2 + ½ O2. The electrolysis of water thus produces a large amount of oxygen which must be purified in order to be able to be used efficiently. In particular, the oxygen produced by electrolysis of water is generally contaminated with co-produced hydrogen, in particular due to the excess of hydrogen permeation through one or more separation membranes or the dissolution of hydrogen in the electrolyte. The water present in the oxygen stream generally comes from gas entrainment, while nitrogen is introduced into the electrolyzer, for example during the inertizing phase at start-up of the electrolyzer and its dissolution in the cold water which is generally pressurized. Thus, the contaminants to be removed from the oxygen stream are hydrogen, nitrogen, water and possibly traces of electrolyte such as KOH.

[0004] In particular, certain industrial applications and processes require oxygen to be as pure as possible, with a purity as high as possible, for example greater than 99%, in order to optimize the effectiveness of said oxygen in these processes or applications.

[0005] The prior art has already provided a number of solutions for significantly removing hydrogen contained in a gas. For example, EP0089183 describes a process for removing hydrogen from a gas which can also contain oxygen. This process involves contacting said gas at room temperature with a catalyst comprising an alumina-tin oxide support impregnated with 0.25 to 2.5% by weight of platinum and 0.25 to 2.5% by weight of palladium. This operation is carried out at room temperature. The hydrogen is oxidized to water, but the water is not removed. The hydrogen content of the input is 0.2 to 2%, and the hydrogen content of the output is 0.04 to 0.09%.

[0006] Y. Jang et al. (“Effect of a modified 13X zeolite support in Pd-Based catalysts for hydrogen oxidation at room temperature”, RSC Adv, 11The influence of palladium-doped modified 13X zeolites for the oxidation of hydrogen to water was investigated by M. S. Shvirov et al. (2021), 38047-38053. More specifically, the authors demonstrated that when 13X zeolites are subjected to an acid treatment and subsequently to a specific calcination, the activity of the catalyst is significantly enhanced. In this article, the zeolite is subjected to an acid treatment, which leads to the degradation of the crystal structure. Therefore, it is not the zeolite that participates in the oxidation of hydrogen to water.

[0007] The catalytic activity of RHO zeolites modified by silver ions is described by the work of O. Yu. Golubeva et al. (“Catalytic hydrogen oxidation using zeolite RHO modified by silver nanoparticles”, Glass Physics and Chemistry, 38 (5), (2012), 455-459). The study shows that the incorporation of large amounts of silver (higher than 17%, expressed as Ag20) in the RHO structure enables the oxidation of hydrogen in air (mainly nitrogen). The reaction occurs at high temperatures (around 200°C). However, there is no mention of the presence or removal of water.

[0008] Currently, the prior art does not provide an acceptable solution. However, it can be considered that nitrogen and water can be easily removed by passing through a CaX type molecular sieve and a 4A type molecular sieve, respectively, but in this case, the separation of hydrogen will be more difficult, since this gas is not adsorbed by the molecular sieves. Therefore, there is currently no acceptable industrial solution for the purification of a gas stream containing oxygen contaminated with hydrogen, water, nitrogen and possibly trace amounts of residual electrolyte.

[0009] Therefore, there is still a need for an oxygen purification method that is easy to industrialize, less costly and easy to implement, in particular an oxygen purification method that is less costly and easier to implement than the prior art. One of the objectives of the present invention is therefore to provide an oxygen purification method that overcomes the drawbacks encountered in the prior art, and in particular to purify oxygen in a simpler way and in particular to remove hydrogen and water present as impurities in the oxygen stream.

[0010] Another objective of the present invention is to provide an oxygen purification method that allows the simultaneous removal of hydrogen and water present as impurities in the oxygen stream, and nitrogen and other impurities such as trace amounts of residual electrolyte such as potassium hydroxide, in particular for an oxygen stream from an electrolytic cell, also called electrolytic oxygen. Other objectives will emerge in the following description of the invention.

[0011] Applicants have now found that it is possible to satisfy all or at least part of the above-mentioned objectives, and in particular in a simple, effective and relatively low-cost manner, by purifying an oxygen stream, in particular an electrolytic oxygen stream, and most particularly while overcoming all or part of the problems encountered in the prior art, by removing or at least substantially reducing the content of hydrogen and the content of water, and where applicable the content of nitrogen and the content of other trace residual electrolytes.

[0012] Unless otherwise indicated in the following disclosure of the application, all numerical ranges are understood to encompass endpoints and, where so used, means both "from" and "to" the indicated number. Unless otherwise indicated, all percentages are mass percentages.

[0013] The present application thus proposes an "integrated" process for purifying and drying oxygen, by removing hydrogen and water using a single zeolite-based adsorbent material, which has been at least partially cation-exchanged and / or impregnated with at least one transition metal.

[0014] More particularly, the subject of the present application is a process for purifying an oxygen stream containing water, hydrogen and possibly nitrogen, comprising:

[0015] - at least one step of contacting the oxygen stream to be purified with a zeolite-based adsorbent material comprising at least one metal in the form of a zero-valent metal, or in oxidized or reduced form, and

[0016] - at least one step of recovering the purified oxygen stream.

[0017] In one embodiment of the application, the oxygen to be purified comprises electrolytic oxygen, i.e. oxygen obtained by electrolysis of water. In a preferred embodiment, the oxygen to be purified comprises mainly oxygen, i.e. from 60 to 99.99 mole% of pure oxygen, preferably from 80 to 99.99 mole% of pure oxygen, more preferably from 90 to 99.99 mole% of pure oxygen, and even more preferably from 95 to 99.99 mole% of pure oxygen, typically from 96.50 to 99.99 mole% of pure oxygen. As mentioned previously, the oxygen to be purified comprises at least water and hydrogen as impurities and possibly nitrogen.

[0018] The zeolite-based adsorbent material used in the present application is a particulate material comprising at least one zeolite, which has been exchanged and / or impregnated with one or more than one metal in the form of a zero-valent metal, or in oxidized or reduced form.

[0019] The term "metal" means metals of the periodic table of elements and in particular metals of columns 3 to 15 of the periodic table of elements, excluding metalloids and non-metals. Preferably, the term "metal" means metals of columns 3 to 14 of the periodic table of elements, excluding metalloids and non-metals, and more preferably, the term "metal" means a metal selected from the group consisting of palladium, platinum, silver, titanium, tin, zinc, nickel, cobalt, iron and copper, as well as lanthanides and actinides, either alone or as a mixture of two or more thereof.

[0020] More preferably, the metal is a metal selected from the group consisting of palladium (Pd), platinum (Pt), copper (Cu), iron (Fe), nickel (Ni), zinc (Zn), tin (Sn), cobalt (Co) and mixtures of two or more thereof in any proportion, and especially preferred are palladium (Pd), platinum (Pt), copper (Cu), nickel (Ni), tin (Sn), iron (Fe) and mixtures of two or more thereof in any proportion. Examples of metal mixtures that can be mentioned include, but are not limited to, Pd / Ni, Pt / Ni, Pd / Pt / Ni, Sn / Pd, Sn / Pt, Sn / Pd / Pt and Cu / Ag.

[0021] It goes without saying that other metals can also be used, but the above-mentioned preferred metals and mixtures thereof prove to be particularly effective and advantageous because of their performance / supply cost ratio.

[0022] Thus, the zeolite-based sorbent material that can be used in the process of the present application comprises at least one zeolite-based sorbent material and at least one metal as described above. The at least one metal can be present in the zeolite-based sorbent material in the original form (or in the metallic form, i.e. zero valence, equal to 0 valence) or in oxidized form or in reduced form, fully or at least partially adsorbed on the at least one zeolite. The metal can also be present in the zeolite-based sorbent material in ionic form, in which case it fully or at least partially contributes to the electrical neutrality of the zeolite-based sorbent material.

[0023] Thus, the zeolite-based sorbent material that can be used in the process of the present application comprises at least one metal as described above, which is capable of being introduced into the zeolite structure, i.e. by deposition and / or impregnation and / or by ion exchange, as described below.

[0024] This introduction is achieved according to conventional methods well known to the person skilled in the art, and generally and preferably by means of one or more aqueous, organic or aqueous-organic salt solutions, at least one of which comprises one or more metal salts, the salt solution(s) preferably being selected from nitrates, acetates, sulfates, etc. of the metal(s).

[0025] The total mass of metal introduced into the zeolite structure is typically and often in the range of 0.1 to 9 mass-%, more typically 0.1 to 7 mass-%, preferably 0.5 to 6 mass-%, more preferably 1 to 5 mass-%, including the boundaries, relative to the total weight of the zeolite-based adsorbent material used in the inventive process. This mass content is measured by X-ray fluorescence (FluoX) analysis as described later in the specification.

[0026] According to a preferred embodiment, in case that the one or more metals are at least partially or completely deposited or impregnated on the zeolite crystals, the particle size of the metal particles is in the range of 1 nm to 250 nm, preferably 5 nm to 250 nm, more preferably 5 nm to 100 nm, still more preferably 5 nm to 50 nm, for example about 15 nm to about 20 nm. This particle size is measured by scanning electron microscopy (SEM) observation with a STEM ("scanning transmission electron microscope") detector.

[0027] As mentioned before, among the preferred metals, copper is preferably used, and in this case the copper content in the zeolite-based adsorbent material used in the inventive process is in the range of 0.1 to 9 mass-%, preferably and often 0.1 to 7 mass-%, preferably 0.5 to 6 mass-%, more preferably 1 to 5 mass-%, including the boundaries, relative to the total weight of the zeolite-based adsorbent material. This content is significantly lower than in the copper-containing zeolite-based adsorbent materials, also called copper-doped zeolite-based adsorbent materials, known in the prior art.

[0028] According to a preferred embodiment, the inventive process employs a zeolite-based adsorbent material containing copper and at least one other metal, preferably the at least one other metal is selected from the group consisting of zinc (Zn) and silver (Ag), just to mention the most common mixtures, also including palladium (Pd), platinum (Pt), iron (Fe), tin (Sn) and cerium (Ce) and mixtures thereof in all proportions. The content of the at least one other metal is typically lower than the copper content, for example about 20 mass-% relative to the mass content of copper, preferably about 10 mass-% relative to the mass content of copper, and more typically 0.1 to 20 mass-% relative to the mass content of copper, often 0.1 to 10 mass-%. However, in certain cases and when desired, the content of the at least one other metal can be greater than or equal to the copper content, in particular equal to the copper content or 1 to 100 mass-% greater than the copper content, advantageously 5 to 70 mass-% greater than the copper content, still more preferably equal to the copper content or 10 to 70 mass-% greater than the copper content.

[0029] According to another preferred embodiment, the process of the present application employs a zeolite-based adsorbent material containing palladium (Pd) and optionally at least one further metal selected from the group consisting of zinc (Zn), silver (Ag) and tin (Sn), only mentioning the most common mixtures, also including platinum (Pt), iron (Fe) and cerium (Ce) and mixtures thereof in all proportions.

[0030] According to another preferred embodiment, the process of the present application employs a zeolite-based adsorbent material containing platinum (Pt) and optionally at least one further metal selected from the group consisting of zinc (Zn), silver (Ag) and tin (Sn), only mentioning the most common mixtures, also including palladium (Pd), iron (Fe) and cerium (Ce) and mixtures thereof in all proportions.

[0031] The at least one zeolite present in the zeolite-based adsorbent material that can be used in the process of the present application can be of any type well known to the person skilled in the art, either natural, artificial (modified natural zeolite) or synthetic (obtained by synthesis). Preferably, the at least one zeolite is selected from the group consisting of LTA zeolites, FAU zeolites, RHO zeolites, MFI zeolites and mixtures of two or more thereof. Most particularly preferred zeolites are selected from the group consisting of FAU type zeolites, MFI type zeolites and mixtures thereof in all proportions and with all Si / Al ratios. Advantageously, reference can be made to the book “Atlas of Zeolite Framework Types”, Elsevier, 5thEdition (2001) to obtain information on the various zeolite types listed above.

[0032] It will be appreciated that the zeolite-based adsorbent material that can be used in the process of the present application can comprise one or more than one zeolite of the same type or of different types, for example a zeolite selected from the group consisting of X type zeolites, Y type zeolites or MFI type zeolites, either alone or as a mixture, for example X zeolite, either alone or in mixture with MFI type zeolite, or for example Y zeolite, either alone or in mixture with MFI type zeolite, or MFI type zeolite alone, or for example X zeolite in mixture with Y zeolite, or for example MFI type zeolite in mixture with X and Y zeolites, to mention just a few illustrative examples, not intended to limit the scope of the present application. Thus, it is also not outside the scope of the present application if the zeolite-based adsorbent material is formed from a structural mixture having different Si / Al molar ratios.

[0033] According to one embodiment of the application, the Si / Al ratio of the zeolite, or the apparent overall ratio of the mixture of zeolites if several zeolites are present in the zeolite-based agglomerate material, can have any value from 1 to 100. According to a preferred aspect, the Si / Al ratio is from 1 to 80, more preferably from 1 to 50, advantageously from 1 to 20. Most preferably, the Si / Al ratio is from 2 to 100, still more preferably from 2 to 80, more preferably from 2 to 50, very advantageously from 2 to 20.

[0034] The zeolite-based adsorbent material that can be used in the process of the application can also comprise a hierarchically porous homolog of the above-mentioned zeolite. Hierarchically porous zeolites are well known to the person skilled in the art and can be prepared, for example, according to the steps described in patent applications WO 2015 / 019013 and WO 2015 / 028740, or by chemical, physical or physico-chemical post-treatment of a conventional zeolite, also known as a non-mesoporous zeolite, which is not hierarchically porous.

[0035] The term "zeolite-based adsorbent material" means a zeolite crystal or a mixture of crystals of different zeolites, optionally agglomerated with one or more than one agglomerating binder well known to the person skilled in the art, for example chosen from the group consisting of alumina, silica and clay. Agglomeration can be carried out before or after one or more operations of introduction of one or more than one metal.

[0036] According to a preferred aspect, the zeolite-based adsorbent material of the application is in the form of agglomerates, i.e. a material in which the crystal or crystals of zeolite(s) are agglomerated by an agglomerating binder, as is well known to the person skilled in the art. The agglomerating binder can be of any type, but for the purposes of the application, the preferred agglomerating binder is chosen from the group consisting of clay, alumina, silicates and mixtures of two or more thereof in any proportion, and preferably, the agglomerating binder is chosen from the group consisting of clay, and more preferably from the group consisting of kaolinic clays, for example kaolin, dickite, halloysite, kaolinite, nacrite, etc.

[0037] The binder ratio, i.e. the ratio of the mass of the agglomerating binder relative to the total weight of the zeolite-based adsorbent material, is within the range known to the person skilled in the art and is generally from 0.1 to 30% by weight, preferably from 1 to 30% by weight, more preferably from 5 to 30% by weight, and advantageously from 10 to 30% by weight.

[0038] When agglomerating the 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, including but not limited to additives well known to those skilled in the art, and in particular additives selected from forming-aid additives, pore formers, silica, carboxymethyl cellulose, etc., and mixtures of two or more thereof in any proportions, to mention only the main additives commonly used when agglomerating zeolite crystals with an agglomeration binder.

[0039] When the binder is a zeolitizable binder, such as kaolin, kaolinite, etc., it can usually and often be fully or partially zeolitized, ie converted into a zeolite, under the action of an alkali such as sodium hydroxide solution, as is well known to those skilled in the art.

[0040] Zeolite-based adsorbent materials suitable for use in the process of the present invention are typically and frequently in the form of beads, but may also take any other shape, such as needles, cylinders, hollow cylinders, disks, trilobes, quadrilobes, extrudates, crushed pieces, and the like.

[0041] The zeolite-based adsorbent material may be of any size and dimension, however zeolite-based adsorbent materials having a volume mean diameter of 0.1 to 10 mm, preferably 0.1 to 5 mm, more preferably 0.5 to 5 mm, advantageously 1 to 5 mm are preferably and frequently used.

[0042] Zeolite-based adsorbent materials suitable for use in the process of the present invention are commercially available or can be obtained using conventional techniques well known to those skilled in the art, starting from procedures known in the literature or on the internet, or techniques that can be readily adapted from such known procedures.

[0043] In one embodiment, the zeolite-based adsorbent material can be readily prepared from zeolite-based adsorbents based on one or more conventional zeolites and / or based on one or more hierarchically porous zeolites, and comprising one or more alkali metal cations and / or alkaline earth metal cations, in particular lithium, sodium, potassium, calcium, strontium or barium, and an agglomerated binder, the agglomerated binder optionally being completely or at least partially zeolitized, the zeolite-based adsorbent being subjected to an impregnation and / or ion exchange treatment with at least one metal as described above, usually in the form of a salt, according to conventional techniques well known to those skilled in the art.

[0044] As a variant, the impregnation and / or ion exchange steps of at least one metal as described above can be carried out directly on the zeolite crystals before agglomeration with the binder and shaping.

[0045] According to a preferred aspect, the method for preparing the zeolite-based adsorbent material that can be used in the context of the present invention comprises at least the following steps:

[0046] a) subjecting the zeolite crystals to one or more cation exchange and / or one or more impregnation with a solution of one or more salts of at least one metal selected from the metals of columns 8 to 15 of the Periodic Table of the Elements, excluding non-metals and metalloids, as described above,

[0047] b) agglomerating with at least one agglomerating binder,

[0048] c) heat treatment (calcination) to harden the agglomerating binder(s),

[0049] d) optionally at least partially zeolitizing the agglomerating binder(s), and

[0050] e) recovering and optionally activating the zeolite-based adsorbent material useful in the context of the present application, typically at 100°C to 550°C.

[0051] In the above process, step a) can be performed one or more times before step b) and / or after step c) and / or step d).

[0052] A calcination step is typically performed, preferably between steps b) and d), typically at a temperature of 400°C to 600°C, although this is not mandatory. As a variant, when a calcination step is performed, step a) can be performed after this calcination step and before step d), whether or not step a) has already been performed before step b).

[0053] According to a preferred embodiment of the process for the preparation of the zeolite-based adsorbent material useful in the process of the present application, a step of shaping the agglomerated material is performed, according to any method well known to the person skilled in the art. This shaping step can be performed during or after the agglomeration step b), and can be followed by step a) of one or more cation exchange and / or impregnation.

[0054] The one or more heat treatment steps in the above process must not result in a significant sintering of the metal atoms, which must be as much as possible dispersed in the zeolite. This can be easily observed by scanning electron microscopy (SEM) or transmission electron microscopy (TEM). It is well known that, in particular, by carefully and strictly controlling the temperature and time of the heat treatment, sintering of the metal atoms can be easily avoided.

[0055] Such a process for the preparation of a zeolite-based adsorbent material exchanged and / or impregnated with one or more than one transition metal is well known by the person skilled in the art and reference can be made for example, but not limited to, EP 1125635 for a precise description of the way the zeolite-based adsorbent material can be prepared for use in the process of the present application, or to the article “Metal Sites in Zeolites: Synthesis, Characterization and Catalysis”, Q. Zhang et al., Chem. Rev. (2023), 123(9), 6039-6106.

[0056] More specifically, the cation exchange can be carried out according to any method well known by the person skilled in the art, for example by contacting the zeolite-based adsorbent material with one or more than one salt solution, preferably an aqueous salt solution, at least one of which comprises one or more than one metal salt; the cation exchange can be single or multiple, and when multiple, the successive exchanges can be carried out with the same or different salt solutions, each exchange step can be preceded and / or followed by at least one washing and / or heat treatment step, said heat treatment can be an oxidative treatment or a reductive treatment.

[0057] The impregnation operation can also be readily carried out according to any method well known by the person skilled in the art, whether wet impregnation or dry impregnation. The term “wet impregnation” refers to contacting the zeolite-based adsorbent material in an aqueous suspension and / or an organic suspension with one or more than one salt solution, preferably an aqueous salt solution, at least one of which comprises one or more than one metal salt, the wet impregnation operation can be preceded and / or followed by at least one heat treatment step, said heat treatment can be an oxidative treatment or a reductive treatment. The term “dry impregnation” refers to contacting the zeolite-based adsorbent material with one or more than one correct volume of a salt solution, preferably an aqueous salt solution, at least one of which comprises one or more than one metal salt, the dry impregnation operation can be preceded and / or followed by at least one heat treatment step, said heat treatment can be an oxidative treatment or a reductive treatment.

[0058] The various steps listed above, cation exchange and / or impregnation, can be carried out once or more than once and can be combined, for example the cation exchange operation can be followed by a wet impregnation or dry impregnation operation and can include a washing step after cation exchange and an optional heat treatment before the impregnation operation.

[0059] These different cation exchange and impregnation operations result in the presence of at least one metal in the form of a cation in the zeolite-based adsorbent material. Prior to use in the process of the present application, if necessary or desired, the valence state of the one or more than one metal can be lowered, possibly to 0 valence, by a reductive elemental treatment, for example and advantageously under a stream of hydrogen.

[0060] Non-limiting examples of zeolite-based adsorbent materials that can be used in the process of the present invention are as follows:

[0061] Sodium MFI (MFI-Na) zeolite or protonated MFI (MFI-H) zeolite having a Si / Al molar ratio of 10 to 20, with a content of 0.1% to 7% of at least one metal selected from the group consisting of Pd, Pt, Ni, Ti, Co, Zn, Ce, Fe, Cu, Sn and Ag, either alone or as a mixture of two or more thereof.

[0062] Sodium FAU (FAU-Na) zeolite or protonated FAU (FAU-H) zeolite having a Si / Al molar ratio of 1.25 to 20, with a content of 0.1% to 7% of at least one metal selected from the group consisting of Pd, Pt, Ni, Ti, Co, Zn, Ce, Fe, Cu, Zn, Sn and Ag, either alone or as a mixture of two or more thereof.

[0063] Sodium LTA (LTA-Na) zeolite or protonated LTA (LTA-H) zeolite having a Si / Al molar ratio equal to 1, with a content ranging from 0.1% to 7% of at least one metal chosen from Pd, Pt, Ni, Ti, Co, Zn, Ce, Fe, Cu, Zn, Sn and Ag, either alone or as a mixture of two or more thereof.

[0064] Sodium RHO (RHO-Na) zeolite or protonated RHO (RHO-H) zeolite having a Si / Al molar ratio of 1 to 20, with a content of 0.1% to 7% of at least one metal selected from the group consisting of Pd, Pt, Ni, Ti, Co, Zn, Ce, Fe, Cu, Zn, Sn and Ag, either alone or as a mixture of two or more thereof.

[0065] According to a preferred embodiment, the zeolite-based adsorbent material used in the present invention is a granular material comprising at least one zeolite exchanged or impregnated with one or more than one metal selected from palladium, platinum, silver, titanium, tin, zinc, nickel, cobalt, iron and copper, in zero-valent metal form, in oxidized form or in reduced form.

[0066] A most particularly preferred embodiment of the process according to the invention uses a zeolite-based adsorbent material in the form of a granular material comprising at least one zeolite which has been exchanged or impregnated with a metal selected from the group consisting of copper, palladium, platinum, iron and zinc, either alone or as a mixture of two or more thereof in all ratios.

[0067] According to yet another preferred embodiment, the inventive process uses a zeolite-based adsorbent material of particulate material, which comprises at least one zeolite of the faujasite (FAU) type, preferably a FAU type zeolite having a Si / Al ratio of 1 to 100, such as a FAU-X type zeolite or a FAU-Y type zeolite, and preferably a FAU-Y type zeolite, which zeolite comprises sodium, and further comprises copper or copper mixed or alloyed with one or more than one metal selected from the group consisting of palladium, platinum, tin, iron and zinc, which one or more than one metal can be exchanged or impregnated in the zeolite-based adsorbent material.

[0068] According to another preferred embodiment, the inventive process uses a zeolite-based adsorbent material of particulate material, which comprises at least one zeolite of the faujasite (FAU) type, preferably a FAU type zeolite having a Si / Al ratio of 2 to 100, such as a FAU-Y type zeolite, which zeolite comprises sodium, and further comprises copper or copper mixed or alloyed with one or more than one metal selected from the group consisting of palladium, platinum, iron, tin and zinc, which one or more than one metal can be exchanged and / or impregnated in the zeolite-based adsorbent material.

[0069] According to yet another preferred embodiment, the inventive process uses a zeolite-based adsorbent material of particulate material, which comprises at least one zeolite of the MFI type, preferably a MFI type zeolite having a Si / Al ratio of 10 to 100, which zeolite comprises sodium, and further comprises copper or copper mixed or alloyed with one or more than one metal selected from the group consisting of palladium, platinum, iron and zinc, which one or more than one metal can be exchanged or impregnated in the zeolite-based adsorbent material.

[0070] In preferred embodiments, examples of zeolite-based adsorbent materials that can be used in the inventive process are:

[0071] protonated FAU

[0072] • a protonated FAU zeolite having a Si / Al ratio of 2 to 10 and a Pd content of 0.1 to 1 wt.-%,

[0073] • a protonated FAU zeolite having a Si / Al ratio of 2 to 10 and a Pt content of 0.1 to 1 wt.-%,

[0074] • a protonated FAU zeolite having a Si / Al ratio of 2 to 10 and a Ni content of 1 to 7 wt.-%,

[0075] • a protonated FAU zeolite having a Si / Al ratio of 2 to 10 and a Ti content of 4 to 7 wt.-%,

[0076] • a protonated FAU zeolite having a Si / Al ratio of 2 to 10 and a Co content of 4 to 7 wt.-%,

[0077] • a protonated FAU zeolite having a Si / Al ratio of 2 to 10 and a Zn content of 4 to 7 wt.-%,

[0078] • a protonated FAU zeolite having a Si / Al ratio of 2 to 10 and a Ce content of 4 to 7 wt.-%,

[0079] • a protonated FAU zeolite having a Si / Al ratio of 2 to 10 and a Fe content of 4 to 7 wt.-%,

[0080] • a protonated FAU zeolite having a Si / Al ratio of 2 to 10 and a Cu content of 4 to 7 wt.-%,

[0081] • a protonated FAU zeolite having a Si / Al ratio of 2 to 10 and a Zn content of 4 to 7 wt.-%,

[0082] • a protonated FAU zeolite having a Si / Al ratio of 2 to 10 and a Sn content of 4 to 7 wt.-%,

[0083] • a protonated FAU zeolite having a Si / Al ratio of 2 to 10 and a Ag content of 4 to 7 wt.-%,

[0084] • a protonated FAU zeolite having a Si / Al ratio of 2 to 10 and a Ti content of 4 to 7 wt.-%,

[0085] • a protonated FAU zeolite having a Si / Al ratio of 2 to 10, a copper content of 2 to 4 wt.-% and a palladium content of 0.1 to 1 wt.-%,

[0086] • a protonated FAU zeolite having a Si / Al ratio of 2 to 10, a copper content of 0.5 to 2 wt.-% and a palladium content of 0.1 to 1 wt.-%,

[0087] • a protonated FAU zeolite having a Si / Al ratio of 2 to 10, a copper content of 0.5 to 2 wt.-% and a platinum content of 0.1 to 1 wt.-%,

[0088] • a protonated FAU zeolite having a Si / Al ratio of 2 to 10, a copper content of 0.5 to 2 wt.-% and a nickel content of 0.1 to 5 wt.-%,

[0089] • a protonated FAU zeolite having a Si / Al ratio of 2 to 10, a copper content of 0.5 to 2 wt.-% and a iron content of 0.1 to 5 wt.-%,

[0090] • a protonated FAU zeolite having a Si / Al ratio of 2 to 10, a copper content of 0.5 to 2 wt.-% and a cobalt content of 0.1 to 1 wt.-%,

[0091] • a protonated FAU zeolite having a Si / Al ratio of 2 to 10, a copper content of 0.5 to 2 wt.-% and a zinc content of 0.1 to 5 wt.-%,

[0092] • a protonated FAU zeolite having a Si / Al ratio of 2 to 10, a copper content of 0.5 to 2 wt.-% and a titanium content of 0.1 to 5 wt.-%,

[0093] • a protonated FAU zeolite having a Si / Al ratio of 2 to 10, a copper content of 0.5 to 2 wt.-% and a tin content of 0.1 to 5 wt.-%.

[0094] sodium FAU

[0095] • a sodium FAU zeolite having a Si / Al ratio of 2 to 10 and a Pd content of 0.1 to 1 wt.-%,

[0096] • a sodium FAU zeolite having a Si / Al ratio of 2 to 10 and a Pt content of 0.1 to 1 wt.-%,

[0097] • a sodium FAU zeolite having a Si / Al ratio of 2 to 10 and a Ni content of 1 to 7 wt.-%,

[0098] • a sodium FAU zeolite having a Si / Al ratio of 2 to 10 and a Ti content of 4 to 7 wt.-%,

[0099] • a sodium FAU zeolite having a Si / Al ratio of 2 to 10 and a Co content of 4 to 7 wt.-%,

[0100] • a sodium FAU zeolite having a Si / Al ratio of 2 to 10 and a Zn content of 4 to 7 wt.-%,

[0101] • a sodium FAU zeolite having a Si / Al ratio of 2 to 10 and a Ce content of 4 to 7 wt.-%,

[0102] • a sodium FAU zeolite having a Si / Al ratio of 2 to 10 and a Fe content of 4 to 7 wt.-%,

[0103] • a sodium FAU zeolite having a Si / Al ratio of 2 to 10 and a Cu content of 4 to 7 wt.-%,

[0104] • a sodium FAU zeolite having a Si / Al ratio of 2 to 10 and a Zn content of 4 to 7 wt.-%,

[0105] • a sodium FAU zeolite having a Si / Al ratio of 2 to 10 and a Sn content of 4 wt.% to 7 wt.%,

[0106] • a sodium FAU zeolite having a Si / Al ratio of 2 to 10 and a Ag content of 4 wt.% to 7 wt.%,

[0107] • a sodium FAU zeolite having a Si / Al ratio of 2 to 10 and a Ti content of 4 wt.% to 7 wt.%,

[0108] • a sodium FAU zeolite having a Si / Al ratio of 2 to 10, a copper content of 2 wt.% to 4 wt.% and a palladium content of 0.1 wt.% to 1 wt.%,

[0109] • a sodium FAU zeolite having a Si / Al ratio of 2 to 10, a copper content of 0.5 wt.% to 2 wt.% and a palladium content of 0.1 wt.% to 1 wt.%,

[0110] • a sodium FAU zeolite having a Si / Al ratio of 2 to 10, a copper content of 0.5 wt.% to 2 wt.% and a platinum content of 0.1 wt.% to 1 wt.%,

[0111] • a sodium FAU zeolite having a Si / Al ratio of 2 to 10, a copper content of 0.5 wt.% to 2 wt.% and a nickel content of 0.1 wt.% to 5 wt.%,

[0112] • a sodium FAU zeolite having a Si / Al ratio of 2 to 10, a copper content of 0.5 wt.% to 2 wt.% and a iron content of 0.1 wt.% to 5 wt.%,

[0113] • a sodium FAU zeolite having a Si / Al ratio of 2 to 10, a copper content of 0.5 wt.% to 2 wt.% and a cobalt content of 0.1 wt.% to 1 wt.%,

[0114] • a sodium FAU zeolite having a Si / Al ratio of 2 to 10, a copper content of 0.5 wt.% to 2 wt.% and a zinc content of 0.1 wt.% to 5 wt.%,

[0115] • a sodium FAU zeolite having a Si / Al ratio of 2 to 10, a copper content of 0.5 wt.% to 2 wt.% and a titanium content of 0.1 wt.% to 5 wt.%,

[0116] • a sodium FAU zeolite having a Si / Al ratio of 2 to 10, a copper content of 0.5 wt.% to 2 wt.% and a tin content of 0.1 wt.% to 5 wt.%.

[0117] Protonated MFI

[0118] • a protonated MFI zeolite having a Si / Al ratio of 10 to 20 and a Pd content of 0.1 to 1 wt.-%,

[0119] • a protonated MFI zeolite having a Si / Al ratio of 10 to 20 and a Pt content of 0.1 to 1 wt.-%,

[0120] • a protonated MFI zeolite having a Si / Al ratio of 10 to 20 and a Ni content of 1 to 7 wt.-%,

[0121] • a protonated MFI zeolite having a Si / Al ratio of 10 to 20 and a Ti content of 4 to 7 wt.-%,

[0122] • a protonated MFI zeolite having a Si / Al ratio of 10 to 20 and a Co content of 4 to 7 wt.-%,

[0123] • a protonated MFI zeolite having a Si / Al ratio of 10 to 20 and a Zn content of 4 to 7 wt.-%,

[0124] • a protonated MFI zeolite having a Si / Al ratio of 10 to 20 and a Ce content of 4 to 7 wt.-%,

[0125] • a protonated MFI zeolite having a Si / Al ratio of 10 to 20 and a Fe content of 4 to 7 wt.-%,

[0126] • a protonated MFI zeolite having a Si / Al ratio of 10 to 20 and a Cu content of 4 to 7 wt.-%,

[0127] • a protonated MFI zeolite having a Si / Al ratio of 10 to 20 and a Zn content of 4 to 7 wt.-%,

[0128] • a protonated MFI zeolite having a Si / Al ratio of 10 to 20 and a Sn content of 4 to 7 wt.-%,

[0129] • a protonated MFI zeolite having a Si / Al ratio of 10 to 20 and a Ag content of 4 to 7 wt.-%,

[0130] • a protonated MFI zeolite having a Si / Al ratio of 10 to 20 and a Ti content of 4 to 7 wt.-%,

[0131] • a protonated MFI zeolite having a Si / Al ratio of 10 to 20, a copper content of 2 to 4 wt.-% and a palladium content of 0.1 to 1 wt.-%,

[0132] • a protonated MFI zeolite having a Si / Al ratio of 10 to 20, a copper content of 0.5 to 2 wt.-% and a palladium content of 0.1 to 1 wt.-%,

[0133] • a protonated MFI zeolite having a Si / Al ratio of 10 to 20, a copper content of 0.5 to 2 wt.-% and a platinum content of 0.1 to 1 wt.-%,

[0134] • a protonated MFI zeolite having a Si / Al ratio of 10 to 20, a copper content of 0.5 to 2 wt.-% and a nickel content of 0.1 to 5 wt.-%,

[0135] • a protonated MFI zeolite having a Si / Al ratio of 10 to 20, a copper content of 0.5 to 2 wt.-% and an iron content of 0.1 to 5 wt.-%,

[0136] • a protonated MFI zeolite having a Si / Al ratio of 10 to 20, a copper content of 0.5 to 2 wt.-% and a cobalt content of 0.1 to 1 wt.-%,

[0137] • a protonated MFI zeolite having a Si / Al ratio of 10 to 20, a copper content of 0.5 to 2 wt.-% and a zinc content of 0.1 to 5 wt.-%,

[0138] • a protonated MFI zeolite having a Si / Al ratio of 10 to 20, a copper content of 0.5 to 2 wt.-% and a titanium content of 0.1 to 5 wt.-%,

[0139] • a protonated MFI zeolite having a Si / Al ratio of 10 to 20, a copper content of 0.5 to 2 wt.-% and a tin content of 0.1 to 5 wt.-%.

[0140] sodium MFI

[0141] • a sodium MFI zeolite having a Si / Al ratio of 10 to 20 and a Pd content of 0.1 to 1 wt.-%,

[0142] • a sodium MFI zeolite having a Si / Al ratio of 10 to 20 and a Pt content of 0.1 to 1 wt.-%,

[0143] • a sodium MFI zeolite having a Si / Al ratio of 10 to 20 and a Ni content of 1 to 7 wt.-%,

[0144] • a sodium MFI zeolite having a Si / Al ratio of 10 to 20 and a Ti content of 4 to 7 wt.-%,

[0145] sodium MFI zeolite having a Si / Al ratio of 10 to 20 and a Co content of 4 to 7% by weight,

[0146] sodium MFI zeolite having a Si / Al ratio of 10 to 20 and a Zn content of 4 to 7% by weight,

[0147] sodium MFI zeolite having a Si / Al ratio of 10 to 20 and a Ce content of 4 to 7% by weight,

[0148] sodium MFI zeolite having a Si / Al ratio of 10 to 20 and an Fe content of 4 to 7% by weight,

[0149] sodium MFI zeolite having a Si / Al ratio of 10 to 20 and a Cu content of 4 to 7% by weight,

[0150] sodium MFI zeolite having a Si / Al ratio of 10 to 20 and a Zn content of 4 to 7% by weight,

[0151] sodium MFI zeolite having a Si / Al ratio of 10 to 20 and a Sn content of 4 to 7% by weight,

[0152] sodium MFI zeolite having a Si / Al ratio of 10 to 20 and an Ag content of 4 to 7% by weight,

[0153] sodium MFI zeolite having a Si / Al ratio of 10 to 20 and a Ti content of 4 to 7% by weight,

[0154] sodium MFI zeolite having a Si / Al ratio of 10 to 20, a copper content of 2 to 4% by weight and a palladium content of 0.1 to 1% by weight,

[0155] sodium MFI zeolite having a Si / Al ratio of 10 to 20, a copper content of 0.5 to 2% by weight and a palladium content of 0.1 to 1% by weight,

[0156] sodium MFI zeolite having a Si / Al ratio of 10 to 20, a copper content of 0.5 to 2% by weight and a platinum content of 0.1 to 1% by weight,

[0157] sodium MFI zeolite having a Si / Al ratio of 10 to 20, a copper content of 0.5 to 2% by weight and a nickel content of 0.1 to 5% by weight,

[0158] sodium MFI zeolite having a Si / Al ratio of 10 to 20, a copper content of 0.5 to 2% by weight and an iron content of 0.1 to 5% by weight,

[0159] • a sodium MFI zeolite having a Si / Al ratio comprised between 10 and 20, a copper content comprised between 0.5 wt% and 2 wt% and a cobalt content comprised between 0.1 wt% and 1 wt%,

[0160] • a sodium MFI zeolite having a Si / Al ratio comprised between 10 and 20, a copper content comprised between 0.5 wt% and 2 wt% and a zinc content comprised between 0.1 wt% and 5 wt%,

[0161] • a sodium MFI zeolite having a Si / Al ratio comprised between 10 and 20, a copper content comprised between 0.5 wt% and 2 wt% and a titanium content comprised between 0.1 wt% and 5 wt%,

[0162] • a sodium MFI zeolite having a Si / Al ratio comprised between 10 and 20, a copper content comprised between 0.5 wt% and 2 wt% and a tin content comprised between 0.1 wt% and 5 wt%.

[0163] As previously mentioned, the method of the present application is an "integrated" oxygen purification method, by removing both hydrogen and water as impurities in the oxygen stream, the oxygen being more specifically an oxygen stream comprising or consisting of electrolytic oxygen.

[0164] The term "integrated" method means that the zeolite-based adsorbent material can simultaneously (i.e. concomitantly) remove both hydrogen and water present in the oxygen stream, at least partially even completely (content below the detection threshold), within the same temperature range. It is well known to the person skilled in the art that zeolites must be operated at high temperatures to remove hydrogen, whereas at high temperatures zeolites adsorb little or no water and will rather tend to desorb water. The "integrated" method of the present application thus has the significant advantage of being able to remove hydrogen and water as well as other possible impurities from the oxygen stream without the need for steps to change the temperature range, thus facilitating the industrial process in terms of time, energy consumption and productivity. It can thus be considered that the method of the present application enables the purification of an oxygen stream without the need for an external supply of energy, for example without the need for an external supply of heat.

[0165] As previously mentioned, the present application relates to a method for purifying an oxygen stream, in particular an electrolytic oxygen stream, said oxygen stream containing hydrogen and water as impurities to be removed, and possibly nitrogen and possibly other impurities inherent to the oxygen synthesis method, in particular the electrolytic oxygen synthesis method.

[0166] The purification process according to the application can thus be carried out according to any gas purification process well known to the person skilled in the art, and more particularly by adsorption of the impurities on the zeolite-based adsorbent material, as previously described. For example, the adsorption process according to the application can be chosen from pressure swing and / or temperature swing processes, typically PSA ("Pressure Swing Adsorption"), PVSA ("Pressure Vacuum Swing Adsorption", using desorption at sub-atmospheric pressure), TSA ("Temperature Swing Adsorption"), PTSA ("Pressure Temperature Swing Adsorption"), PVTSA ("Pressure Vacuum Temperature Swing Adsorption", using desorption at sub-atmospheric pressure).

[0167] The fluid to be purified mainly contains oxygen, as previously described, as well as water, hydrogen and possibly nitrogen. The water content is generally between 20 ppmv and 1.5 mole%, preferably between 50 ppmv and 1.5 mole%, more preferably between 100 ppmv and 1.5 mole%, advantageously between 200 ppmv and 1.5 mole%. The hydrogen content in the stream is generally between 5 ppmv and 1 mole%, preferably between 5 ppmv and 5000 ppmv, more preferably between 5 ppmv and 3000 ppmv, still more preferably between 5 ppmv and 1000 ppmv. The nitrogen content is between 0 and 1 mole%, generally between 10 ppmv and 1 mole%.

[0168] The purification process according to the application can be carried out according to any conventional gas separation process, for example by means of one or more than one column comprising at least one bed of zeolite-based adsorbent material as described above (also called "one or more than one adsorber" or simply "one or more than one reactor"). According to one embodiment, the process according to the application employs at least two adsorbers, in particular when operated in continuous flow, by techniques well known to the person skilled in the art.

[0169] The pressure at which the fluid to be purified is brought into contact with the zeolite-based adsorbent material is thus 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 the temperature is 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.

[0170] In a preferred embodiment, the bed of zeolite-based adsorbent material is regenerated after the adsorption phase, i.e. desorption is carried out by pressure reduction and countercurrent discharge (PSA process and VPSA process) or by temperature reduction (TSA process), optionally combined with pressure reduction and countercurrent discharge (PVTSA process).

[0171] For PSA and VPSA processes, the desorption pressure is typically comprised between 0.1 MPa and 1 MPa and between 500 Pa and 95 kPa, respectively. Typically, the desorption temperature is close to the adsorption temperature for obvious reasons of ease of operation and energy saving, in other words, no intentional temperature change is usually performed.

[0172] According to yet another preferred embodiment of the application, a purge phase can be performed at the end of the desorption phase, typically by reintroducing part of the purified gas in counter-current, typically less than 20% of the flow generated by the adsorbers.

[0173] It should also be understood that the process of the application can also comprise one or more than one pressure equalization phase between any different adsorbers. One or more than one pressure equalization phase can advantageously be performed between the adsorption phase and the desorption phase, according to techniques equally well known by the person skilled in the art. The advantage of providing one or more than one pressure equalization phase lies especially in minimizing the loss of oxygen as well as hydrogen throughout the process. Also, it can be considered to recover the gas collected during the desorption process, which is common in hydrogen PSA processes.

[0174] For TSA and PVTSA processes, part of the purified gas, typically less than 20% of the flow generated by the adsorbers, is heated to a temperature comprised between 40°C and 250°C, then injected in counter-current into the adsorbers, possibly at a pressure lower than the adsorption phase (PVTSA), i.e. between 1 kPa and 3 MPa. As for PSA and VPSA, different pressure equalization configurations and purge configurations can be considered.

[0175] In the process of the application, the adsorption phase and the desorption phase are performed cyclically. The process can optionally comprise a cooling system integrated in the adsorbers to avoid or at least minimize the excessive heating of the adsorption beds, which would inhibit the adsorption of water by the particulate zeolite-based adsorbent material, as previously mentioned. The process can also comprise a step of drying the gas stream before and / or after passing through the zeolite-based adsorbent material comprising at least one metal according to the application.

[0176] Being able to dry, i.e. adsorb, the water present or formed on the same material, will simplify the process downstream of the electrolyzer, while producing an oxygen stream of high purity, which is particularly required for many fields of application.

[0177] The method of the present application thus has many advantages, most particularly the ability to simultaneously reduce the dissolved hydrogen in the oxygen stream and adsorb the water already present in the oxygen stream and the water formed by reduction of the dissolved oxygen. The method of the present application thus enables the easy, industrial production of a high purity oxygen stream, in particular an oxygen stream having a purity greater than 99%, more particularly an electrolytic oxygen stream having a purity greater than 99% and a hydrogen content less than 5 ppmv, a water content less than 1 ppmv, these impurity contents being determined according to conventional techniques well known to the person skilled in the art, for example using an ionization mass spectrometer.

[0178] According to another aspect of the present application, it relates to the purified oxygen stream obtained according to the aforementioned method, and its use as an industrial product or reagent in various fields, for example the metallurgical field or the medical field, just to mention some known applications. It is worth noting that one of its main advantages is the ability to provide oxygen free or almost free of hydrogen, for obvious safety reasons.

[0179] According to another aspect, the present application relates to the use of a zeolite-based adsorbent material as defined previously for the purification of an oxygen stream, in particular for the purification of electrolytic oxygen.

[0180] According to yet another aspect, the present application relates to a method for the preparation of high purity oxygen, comprising at least the following steps:

[0181] 1) electrolysis of an aqueous solution comprising mainly hydrogen oxides to produce a hydrogen stream and an oxygen stream,

[0182] 2) recovery of the oxygen stream from the electrolysis step 1),

[0183] 3) purification of the oxygen stream recovered in step 2) by passing the oxygen stream recovered in step 2) through a zeolite-based adsorbent material as defined previously, and

[0184] 4) recovery of the high purity oxygen.

[0185] It will be understood that the method for the preparation of high purity oxygen according to the present application comprises the electrolysis step 1), which can be carried out in a conventional manner well known to the person skilled in the art.

[0186] This method thus enables the production of oxygen of extremely high purity in an efficient and economical manner, and in particular more economically than the synthesis methods known to date for the preparation of oxygen by water electrolysis.

[0187] Analytical techniques

[0188] Si / Al molar ratio and degree of exchange

[0189] The Si / Al molar ratio and the degree of exchange are measured by any chemical analysis technique known to the person skilled in the art. Among these techniques, the chemical analysis technique that can be mentioned is X-ray fluorescence, as described in standard NF EN ISO 12677:2011, which uses a wavelength dispersive spectrometer (WDXRF), such as the Tiger S8 machine from the company Bruker.

[0190] X-ray fluorescence is a spectroscopic technique that makes use of the photoemission of atoms in the X-ray range to determine the elemental composition of a sample. The atoms are usually excited by an X-ray beam or electron bombardment, producing specific radiation after the atoms return to the ground state. The advantage of X-ray fluorescence spectroscopy is that it is almost independent of the chemical combination of the elements, thus providing accurate determination both quantitatively and qualitatively. A measurement uncertainty of less than 0.4% by weight is generally obtained after calibration for each oxide.

[0191] These elemental chemical analyses can check the Si / Al molar ratio of the starting zeolite, the content of one or more than one deposited metal and the amount of ion exchange. In the description of the application, the measurement uncertainty of the Si / Al molar ratio is ± 5%. The amount of ion exchange is related to the number of moles of sodium oxide Na2O remaining in the agglomerated zeolite-based adsorbent after exchange. It should be noted that the content of the various oxides is given in weight percentage relative to the total weight of the anhydrous zeolite-based adsorbent material.

[0192] The Si / Al molar ratio of the zeolite in the zeolite-based adsorbent material is measured by solid-state silicon nuclear magnetic resonance (NMR) spectroscopy. In the description of the application, the measurement uncertainty of the Si / Al molar ratio is ± 5%.

[0193] Metal content

[0194] The content of the metal present in the zeolite-based adsorbent material is also obtained by X-ray fluorescence analysis described above and is expressed in mass percentage of metal.

[0195] Particle size of the metal

[0196] The number average diameter of the metal particles contained in the zeolite-based adsorbent material is estimated by scanning electron microscopy (SEM) observation.

[0197] To estimate the size of the metal particles in the sample, a set of images is acquired at a magnification of at least 5000x. The diameter of at least 200 particles is then measured using a dedicated software, such as the Smile View software published by LoGraMi. The precision is about 3%. The standard deviation s of the distribution is determined simultaneously by the histogram measurement formed by said diameter measurements.

[0198] Particle size of the zeolite-based adsorbent:

[0199] The volume average diameter of the zeolite-based adsorbent is determined according to standard ISO 13322-2:2006 by imaging analysis of the particle size distribution of the agglomerate sample, using a conveyor belt to pass the sample in front of the camera objective.

[0200] The volume average diameter is then calculated from the particle size distribution according to standard ISO 9276-2:2001. In this document, the term "volume average diameter" or "size" is used for the zeolite-based agglomerates. The precision is about 0.01 mm for the size range of the agglomerates of the present invention.

[0201] Qualitative analysis by X-ray diffraction

[0202] The purity of the zeolite in the zeolite-based adsorbent material is evaluated by X-ray diffraction analysis, known by the acronym XRD to the person skilled in the art. This determination is carried out on an XRD machine of the Bruker brand.

[0203] This analysis makes it possible to identify the various zeolites present in the adsorbent material, since each zeolite structure has a unique diffraction pattern, defined by the position of the diffraction peaks and their relative intensities.

[0204] Before the measurement, the zeolite-based material is ground, then spread out and flattened on the sample holder by simple mechanical compression.

[0205] The conditions for acquiring the diffraction pattern on a Bruker D5000 instrument are as follows:

[0206] • the Cu tube used is 40 kV - 30 mA;

[0207] • the slit sizes (divergence slit, scattering slit and analysis slit) = 0.6 mm;

[0208] • the filter: Ni;

[0209] • the sample holder rotation speed: 15 rpm;

[0210] • the measurement range: 3° < 2Q < 50°;

[0211] • the step: 0.02°;

[0212] • the counting time per step: 2 seconds.

[0213] The diffraction pattern obtained is interpreted using the EVA software and the zeolites are identified with the aid of the ICDD PDF-2 database in version 2011.

[0214] Microcrystallinity in terms of Dubinin volume

[0215] Dubinin volume (or micropore volume V mi) in a manner conventional to the person skilled in the art, in particular by measuring the adsorption isotherm of a gas, for example nitrogen, argon, oxygen, etc., at its liquefaction temperature. Nitrogen is preferably used. Prior to carrying out the adsorption measurement, the zeolite crystals of the application are degassed at a reduced pressure (pressure < 6.7 x 10 -4 Pa) at 300°C to 450°C for 9 hours to 16 hours. For example, for a zeolite of MFI type or of FAU type, the nitrogen adsorption isotherm at 77 K is then measured on a Micromeritics ASAP2020 instrument, taking at least 35 measurement points for a relative pressure P / Po ratio of 0.002 to 1. The micropore volume is determined according to the standard ISO 15901-3:2007 from the isotherm obtained by applying the Dubinin-Raduskevitch equation. The micropore volume thus evaluated is expressed in cm 3 of liquid adsorbent per gram of anhydrous adsorbent. The measurement uncertainty is ± 0.003 cm 3 .g -1 .

[0216] According to an embodiment of the application

[0217] The oxygen stream recovered from the electrolysis cell has a temperature of 50°C. The oxygen stream is pressurized to 0.8 MPa. The oxygen stream contains 3000 ppmv of hydrogen and 1000 ppmv of water.

[0218] The electrolysis oxygen stream to be purified is introduced into a column containing 1 liter of zeolite-based adsorbent material. The contact time between the stream and the zeolite-based adsorbent material is set to 10 seconds. The zeolite-based adsorbent material is formed from beads of 1 mm in diameter obtained by agglomeration with 20% by weight of binder and H-MFI (protonated MFI) zeolite crystals having a Si / Al ratio equal to 12.5 and a Pd content of 0.3% by weight.

[0219] The purified oxygen stream recovered at the outlet of the column is analyzed using an ionization mass spectrometer. The residual water content is confirmed by a humidity probe from the company Panametrics. The oxygen thus purified contains 0.3 ppmv of water and the amount of residual hydrogen is below the detection threshold.

Claims

1. A method for purifying an oxygen stream containing water, hydrogen and possibly nitrogen, comprising: at least one step of contacting the oxygen stream to be purified with a zeolite-based adsorbent material comprising at least one metal in zero-valent metallic form, in oxidized form or in reduced form, and - at least one recovery step of a purified oxygen stream.

2. The method according to claim 1, wherein the oxygen to be purified comprises electrolytic oxygen.

3. The method according to claim 1 or 2, wherein the oxygen to be purified comprises 60 mol% to 99.99 mol% pure oxygen, preferably 80 mol% to 99.99 mol% pure oxygen, more preferably 90 mol% to 99.99 mol% pure oxygen, and even more preferably 95 mol% to 99.99 mol% pure oxygen, typically 96.50 mol% to 99.99 mol% pure oxygen, and contains at least water and hydrogen as impurities, and possibly also nitrogen.

4. The process according to any one of the preceding claims, wherein the at least one transition metal is selected from the metals of columns 3 to 15 of the Periodic Table of the Elements, excluding metalloids and non-metals, preferably from the metals of columns 3 to 14 of the Periodic Table of the Elements, excluding metalloids and non-metals, and more preferably from palladium, platinum, silver, titanium, tin, zinc, nickel, cobalt, iron and copper, and the metal is present alone or as a mixture of two or more thereof.

5. The process according to any one of the preceding claims, wherein the zeolite-based adsorbent material comprises at least one zeolite selected from the group consisting of LTA zeolites, FAU zeolites, RHO zeolites and MFI zeolites and mixtures of two or more thereof in all proportions and at all Si / Al ratios, and preferably selected from the group consisting of FAU-type zeolites, MFI-type zeolites and mixtures thereof in all proportions and at all Si / Al ratios.

6. The method according to any one of the preceding claims, wherein the zeolite-based adsorbent material comprises at least one zeolite selected from the group consisting of FAU-type zeolites, MFI-type zeolites, and mixtures thereof, and at least one metal in zero-valent metallic form, in oxidized form, or in reduced form, selected from the group consisting of copper, palladium, platinum, tin, iron, and zinc, and mixtures thereof, one or more than one of the metals being capable of being exchanged or impregnated into the zeolite-based adsorbent material.

7. The process according to claim 1 , wherein the oxygen stream to be purified is contacted with the zeolite-based adsorbent material at a pressure of 0.5 to 5 MPa, preferably 0.9 to 5 MPa, more preferably 1.5 to 5 MPa, and at a temperature of 10 to 100° C., preferably 15 to 90° C., advantageously 20 to 60° C., typically 25 to 55° C.

8. Use of a zeolite-based adsorbent material for purifying an oxygen stream, and in particular for purifying electrolytic oxygen, the zeolite-based adsorbent material comprising at least one metal in zero-valent metallic form, in oxidized form or in reduced form, wherein the at least one metal is selected from the metals of columns 3 to 15 of the Periodic Table of the Elements, excluding metalloids and non-metals, preferably from the metals of columns 3 to 14 of the Periodic Table of the Elements, excluding metalloids and non-metals, and more preferably from palladium, platinum, silver, titanium, tin, zinc, nickel, cobalt, iron and copper, alone or as a mixture of two or more thereof.

9. Use of the purified oxygen stream obtained by the process according to any one of claims 1 to 7 as an industrial product or reagent.

10. A method for producing high-purity oxygen, comprising at least the following steps: 1) electrolyzing an aqueous solution comprising mainly hydrogen oxides to produce a hydrogen gas stream and an oxygen gas stream, 2) recovering the oxygen stream from the electrolysis step 1), 3) purifying the oxygen stream recovered in step 2) by passing the oxygen stream recovered in step 2) through a zeolite-based adsorbent material according to the process of any one of claims 1 to 7, and 4) Recover high-purity oxygen.