Electrolytic hydrogen purification

Abstract

The present invention relates to a method for purifying a hydrogen stream contaminated with water, oxygen, and optionally nitrogen, said method comprising contacting the hydrogen stream to be purified with a zeolitic adsorbent material comprising at least one metal selected from the metals of columns 3 to 12 of the periodic table of the elements in zero-valent metallic form or in oxidized or reduced form, and recovering the purified hydrogen stream. The present invention also relates to the use of a zeolitic adsorbent material containing at least one metal from columns 3 to 12 of the periodic table of the elements for the purification of hydrogen, and the use of the hydrogen thus purified in an industrial process.

Description

[Technical Field]

[0001] The present invention relates to a method for purifying hydrogen from an electrolytic cell, and more particularly to a method for purifying hydrogen containing water and oxygen, and optionally trace amounts of nitrogen and / or trace amounts of residual electrolyte, such as potassium hydroxide. [Background technology]

[0002] A significant portion of the hydrogen produced industrially today is obtained by steam reforming. However, ecological constraints related to global warming have prompted scientists to reconsider water electrolysis for hydrogen production. One drawback of water electrolysis is that the hydrogen produced contains different contaminants than that produced by steam reforming, particularly oxygen, nitrogen, and water.

[0003] In particular, hydrogen produced by water electrolysis is frequently contaminated with co-produced oxygen, especially due to excessive oxygen permeation through the separation membrane or dissolution of oxygen in the electrolyte. Water present in the hydrogen stream generally originates from gas entrainment, while nitrogen originates, for example, from the passivation phase during start-up of the electrolyzer and from dissolution in cold water introduced into the electrolyzer, often under pressure.

[0004] These contaminants must all be removed, since most, if not all, uses of hydrogen require a very pure gas, for example when hydrogen is used in the electrical or electronic fields, especially in fuel cells. In particular, in this type of use, contamination with oxygen above 5 ppm reduces the effectiveness of the fuel cell. Furthermore, the possible presence of nitrogen (for example, if the water used is insufficiently degassed) can affect the function and output of downstream fuel cells. Therefore, it is important to have very pure hydrogen available.

[0005] The prior art has already provided numerous solutions for obtaining very pure hydrogen. In particular, US Patent No. 1,142,0869 may be mentioned, which describes the purification of a hydrogen-containing hydrocarbon and oxygen stream by PSA (an abbreviation for "Pressure Swing Adsorption"). The streams thus purified contain, for example, methane, C2-C3 hydrocarbons, and also traces of nitrogen, carbon monoxide, and oxygen. These may be, for example, streams from a propane dehydrogenation unit.

[0006] Typically, hydrocarbon removal is done with activated carbon, oxygen and carbon monoxide are removed by catalytic reaction on a layer of copper-impregnated alumina, and water and CO2 produced by the catalytic reaction are removed by another layer of activated carbon.

[0007] US Patent Application Publication No. 2019 / 0247781 proposes the specific removal of oxygen using palladium (Pd), platinum (Pt), or copper (Cu) based catalysts on alumina to reduce oxygen prior to purification in a PSA (known as a "DEOXO" unit).

[0008] Additionally, Ligen et al., “Energy efficient hydrogen drying and purification for fuel cell vehicles,” Int. J. Hydrogen Energy, (2020), 45, 10639 sqq., details the combined use of a DEOXO+VPSA (“Volume and Pressure Swing Adsorption”) unit to purify the hydrogen stream from an alkaline electrolyzer.

[0009] However, one drawback associated with the prior art is that oxygen is only weakly or very weakly adsorbed by most of the adsorbents commonly used in PSA hydrogen technology, namely, activated carbon, alumina, silica gel, and 5A or 13X molecular sieves. Therefore, the solution currently adopted in the industry to remove oxygen from the hydrogen matrix is ​​to use a DEOXO unit, in which oxygen is reduced with water, typically copper-impregnated alumina. The water is then removed by a PSA drying process. Consequently, at least two units are required to purify the oxygen-containing hydrogen matrix, which results in significant installation and energy costs.

[0010] US Patent Application Publication No. 2021 / 309517 describes a purification method by adsorption onto a bed consisting of at least one layer of a reduction catalyst based on supported Cu, Pd, or Pt, which is regenerated by countercurrent circulation of oxygen-free, hydrogen-rich gas via a PSA or TSA (Temperature Swing Adsorption) process. The preferred catalyst is alumina impregnated with at least 10% copper by mass. This is preferably used in a three-layer configuration: the first layer of adsorbent dries the stream (silica gel, activated alumina, 13X), the second layer (copper-impregnated alumina) removes oxygen by an exothermic catalytic reaction (O + H ←→ H O), and the third layer (silica gel, activated alumina, 13X, CaX, 5A) removes water produced as the stream passes over the second layer, and optionally also removes nitrogen.

[0011] This solution consists of a single treatment bed with several layers of material (adsorbent and catalyst) and is an improvement, but is somewhat complex and expensive due to the use of several materials and an alumina-based catalyst heavily loaded with copper. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] U.S. Patent No. 1,142,0869 [Patent Document 2] US Patent Application Publication No. 2019 / 0247781 [Patent Document 3] U.S. Patent Application Publication No. 2021 / 309517 [Non-patent literature]

[0013] [Non-Patent Document 1] Ligen et al., “Energy efficient hydrogen drying and purification for fuel cell vehicles”, Int. J.Hydrogen Energy, (2020), 45, 10639 sqq. Summary of the Invention [Problem to be solved by the invention]

[0014] Therefore, there remains a need for a hydrogen purification method that is readily industrializable, inexpensive, and easy to implement, and in particular a hydrogen purification method that is cheaper and easier to implement than the techniques known today.It is therefore an object of the present invention to provide a hydrogen purification method that overcomes the drawbacks encountered in the prior art, in particular to purify hydrogen in a simpler way, and in particular to remove both oxygen and water that are present as impurities in the hydrogen stream.

[0015] Another object of the present invention is to provide a hydrogen purification method that allows for the simultaneous removal of oxygen and water present as impurities in the hydrogen stream, as well as other impurities such as nitrogen and trace amounts of residual electrolyte, e.g., potassium hydroxide, particularly in a hydrogen stream from an electrolytic cell, also referred to as electrolytic hydrogen. Other objects will become apparent in light of the following description of the invention.

[0016] The applicant has now found that it is possible to purify hydrogen streams, in particular electrolytic hydrogen streams, by meeting all or at least some of the objectives disclosed above, in particular by removing or at least significantly reducing the content of oxygen and water, and, where appropriate, the content of nitrogen and other traces of residual electrolyte, in a simple, effective and relatively inexpensive manner, and most particularly by overcoming all or some of the problems encountered in the prior art.

[0017] Unless otherwise indicated in the following disclosure of the invention, all ranges of values, particularly those identified by "between" or "from," are understood to be inclusive. Unless otherwise specified, all percentages are percentages by weight.

[0018] The present invention therefore proposes an "all-in-one" method for purifying hydrogen by removing both oxygen and water using a single zeolitic adsorbent material, in which the zeolite has at least partially undergone cation exchange and / or impregnation with at least one metal from columns 3 to 12 of the periodic table of the elements. [Means for solving the problem]

[0019] The subject of the present invention is more particularly a method for purifying a hydrogen stream containing water, oxygen and optionally nitrogen, comprising: - at least one step of contacting the hydrogen stream to be purified with a zeolitic adsorbent material containing at least one metal from columns 3 to 12 of the periodic table of the elements in zero-valent metallic form or in oxidized or reduced form, and - recovering at least one purified hydrogen stream. DETAILED DESCRIPTION OF THE INVENTION

[0020] In one embodiment of the present invention, the hydrogen to be purified comprises electrolytic hydrogen, i.e., hydrogen obtained by electrolysis of water. In a preferred embodiment, the hydrogen to be purified comprises primarily hydrogen, i.e., 60 mol% to 99.99 mol% pure hydrogen, preferably 80 mol% to 99.99 mol% pure hydrogen, more preferably 90 mol% to 99.99 mol% pure hydrogen, even more preferentially 95 mol% to 99.99 mol% pure hydrogen, and typically 96.50 mol% to 99.99 mol% pure hydrogen. As mentioned above, the hydrogen to be purified contains at least water and oxygen as impurities, and in some cases also contains nitrogen.

[0021] The zeolitic adsorbent material used in the present invention is a particulate material comprising at least one zeolite exchanged and / or impregnated with one or more metals from columns 3 to 12 of the periodic table of the elements in their zero-valent metal form or in their oxidized or reduced form.

[0022] The term "metals from columns 3 to 12 of the periodic table of the elements" means transition metals (columns 3 to 11 of the periodic table of the elements), including the lanthanides and actinides, and metals from column 12 of the periodic table of the elements, in particular those selected from the transition metals (columns 3 to 11 of the periodic table of the elements), zinc and cerium, more preferably iron, cobalt, cerium, nickel, titanium, copper, zinc, palladium, silver and platinum, either alone or as a mixture of two or more thereof.

[0023] According to a preferred embodiment, the metal is selected from the metals of columns 8 to 12 of the periodic table of the elements, as well as titanium and cerium, either alone or as a mixture of two or more thereof. In yet another preferred embodiment, the metal is selected from copper, iron, and zinc, either alone or as a mixture, optionally with one or more metals selected from palladium, silver, and platinum. Of these metals, copper is most particularly preferred. Mixtures of copper / palladium, copper / silver, and copper / platinum are also preferred.

[0024] Of course, other metals may be used, but the preferred metals and metal mixtures listed above have been found to be the most particularly effective and advantageous in terms of their effectiveness / supply cost ratio.

[0025] The zeolitic adsorbent material that can be used in the method of the present invention consequently comprises at least one zeolitic adsorbent material and at least one metal, as disclosed above. The at least one metal may be present in the zeolitic adsorbent material in its native form (or metallic form, i.e., zero valence, equal to 0) or oxidized form, fully or at least partially adsorbed on the at least one zeolite, or may be present in its reduced form. The metal may also be present in the zeolitic adsorbent material in ionic form, in which case the metal contributes in whole or at least in part to the electronic neutrality of the zeolitic adsorbent material.

[0026] Thus, the zeolitic adsorbent material that can be used in the process of the present invention comprises at least one metal as defined above, which can be provided in the zeolite structure, i.e., deposited and / or impregnated and / or included by ion exchange, as described below.

[0027] This provision can be achieved according to conventional methods well known to those skilled in the art, and is generally and advantageously achieved by means of one or more aqueous, organic or aqueous-organic salt solutions, at least one of which contains one or more metal salts, preferably selected from nitrates, acetates, sulfates, etc. of said metals.

[0028] The total mass of metals provided in the zeolitic structure is generally between 0.1% and 9%, preferably between 0.5% and 8%, more preferably between 1% and 6%, inclusive, of the total weight of the zeolitic adsorbent material used in the process of the present invention, as determined by X-ray fluorescence (FluoX) analysis, as described later in this specification.

[0029] According to a preferred embodiment, when the metal is at least partially or completely deposited or impregnated into the zeolite crystals, the particle size of the metal particles is 1 nm to 250 nm, preferably 5 nm to 250 nm, more preferably 5 nm to 100 nm, even more preferably 5 nm to 50 nm, for example about 15 nm to 20 nm, as determined by observation with a scanning electron microscope (SEM) equipped with a STEM ("scanning transmission electron microscope") detector.

[0030] As mentioned above, among the preferred metals, copper is preferably used, and in this case, the copper content in the zeolitic adsorbent material used in the process of the present invention is preferably, usually inclusively, 0.1% to 9% by mass, preferably 0.5% to 8% by mass, more preferably 1% to 6% by mass, based on the total weight of the zeolitic adsorbent material, which is particularly significantly lower than that encountered in copper-containing zeolitic adsorbent materials known from the prior art, also known as copper-doped zeolitic adsorbents.

[0031] According to a preferred embodiment, the method of the present invention is carried out using a zeolitic adsorbent material containing copper and at least one other metal, preferably at least one other metal selected from palladium (Pd), platinum (Pt), nickel (Ni), iron (Fe), zinc (Zn), and mixtures thereof, in any proportion. The content of the at least one other metal is generally lower than the copper content, e.g., about 20% by mass relative to the copper content, preferably about 10% by mass relative to the copper content, more typically 0.1% to 20% by mass relative to the copper content, and typically 0.1% to 10% by mass. However, the content of the at least one other metal may, in some cases, when desired, be equal to or greater than the copper content, particularly 1% to 100% by mass or more relative to the copper content, advantageously 5% to 70% by mass or more, and even better 10% to 70% by mass or more.

[0032] The at least one zeolite present in the zeolitic adsorbent material that can be used in the process of the present invention may be of any type known to those skilled in the art, and may be natural, artificial (modified natural zeolite), or synthetic (synthetically obtained). Preferably, the at least one zeolite is selected from LTA, FAU, RHO, MFI zeolites, and mixtures of two or more thereof. Most particularly preferred are zeolites selected from FAU-type zeolites, MFI-type zeolites, and mixtures thereof, in all proportions and with all Si / Al ratios. Advantageously, for information on the various zeolite types listed above, reference may be made to the book "Atlas of Zeolite Framework Types", Elsevier, 5th edition (2001).

[0033] It will be understood that the zeolitic adsorbent material that may be used in the process of the present invention may comprise one or more zeolites of the same or different types, such as X zeolite alone or together with MFI zeolite, or X zeolite having a Si / Al ratio of about 1.25 and X zeolite having a Si / Al ratio of about 1, or Y zeolite alone or MFI zeolite, to name a few simple illustrative examples only, and are not intended to limit the scope of the present invention in any way. Consequently, it would not depart from the context of the present invention if the zeolite were formed from a mixture of structures having different Si / Al molar ratios.

[0034] According to one embodiment of the present invention, the Si / Al ratio of the zeolite, or the apparent overall ratio of the mixture of zeolites if several are present in the zeolitic aggregate material, may have any value between 1 and 100. According to a preferred embodiment, this Si / Al ratio is between 1 and 80, more preferably between 1 and 50, advantageously between 1 and 20.

[0035] Zeolitic adsorbent materials that can be used in the process of the present invention can also include hierarchically porous homologs of the above-listed zeolites. Hierarchically porous zeolites are well known to those skilled in the art and can be prepared, for example, according to the procedures described in patent applications WO 2015 / 019013 and WO 2015 / 028740, or by chemical, physical, or physicochemical post-treatment of conventional zeolites that are not hierarchically porous, also known as non-mesoporous zeolites.

[0036] The term "zeolitic adsorbent material" means zeolite crystals or a mixture of crystals of different zeolites, optionally agglomerated with one or more agglomerating binders well known to those skilled in the art, for example selected from alumina, silica, and clay. Agglomeration may be carried out before or after the operation to deliver the metals.

[0037] According to a preferred embodiment, the zeolitic adsorbent material of the present invention is in the form of an aggregate, i.e., a material in which zeolite crystals have been aggregated with the aid of an aggregate binder, as is fully known to those skilled in the art. The aggregate binder may be of any type, but for the purposes of the present invention, aggregate binders selected from clays, aluminas, silicates, and mixtures of two or more thereof in any proportion are preferred, preferably the aggregate binder is selected from clays, more preferably from kaolin clays such as kaolin, dickite, halloysite, kaolinite, nacrite, etc.

[0038] The binder ratio, i.e. the mass of the agglomerate binder relative to the total weight of the zeolitic adsorbent material, is within the range known to those skilled in the art and is generally between 0.1% and 30% by weight, preferably between 1% and 30%, more preferably between 5% and 30%, advantageously between 10% and 30%.

[0039] When the zeolite crystals are agglomerated with at least one agglomerating 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, by way of illustrative and non-limiting examples only, the main additives commonly used when agglomerating zeolite crystals with agglomerating binders, in particular additives selected in any proportion from molding aids, pore formers, silica, carboxymethylcellulose, and the like, and mixtures of two or more thereof.

[0040] If the binder is a zeolitizable binder, such as kaolin, kaolinite, etc., it can be totally or partially zeolitized, i.e. converted into zeolite, as is well known to those skilled in the art, generally and usually under the action of a base, for example sodium hydroxide solution.

[0041] Zeolitic adsorbent materials suitable for use in the process of the present invention are generally usually in the form of beads, but can take any other shape, such as needles, cylinders, hollow cylinders, discs, trilobes, tetralobes, extrudates, crushed forms, and other forms.

[0042] The zeolitic adsorbent material can have any size and dimension, but zeolitic adsorbent materials having a volume average diameter of 0.1 mm to 10 mm, preferably 0.1 mm to 5 mm, more preferably 0.5 mm to 5 mm, advantageously 1 mm to 5 mm are preferred and commonly used.

[0043] Zeolitic adsorbent materials suitable for use in the process of the present invention are either commercially available or can be obtained using conventional techniques well known to those skilled in the art, or techniques that can be easily adapted from known operating procedures obtained from the literature or the internet.

[0044] In one embodiment, the zeolitic adsorbent material can be readily prepared from a zeolitic adsorbent, based on conventional zeolites and / or based on hierarchically porous zeolites, comprising one or more alkali metal and / or alkaline earth metal cations, in particular lithium, sodium, potassium, calcium, strontium or barium, and optionally a fully or at least partially zeolitic aggregate binder, which zeolitic adsorbent is subjected to an impregnation and / or ion exchange treatment with at least one metal as defined above, generally in salt form, according to conventional techniques well known to those skilled in the art.

[0045] Alternatively, a step of impregnation and / or ion exchange with at least one metal as defined above may be carried out directly on the zeolite crystals before agglomeration and shaping with the binder.

[0046] According to a preferred embodiment, the method for preparing a zeolitic adsorbent material that can be used in the context of the present invention comprises at least the following steps: a) one or more cation exchanges and / or impregnations of zeolite crystals with one or more salt solutions of at least one metal selected from the metals of columns 8 to 12 of the periodic table of the elements, as defined above; b) flocculation with at least one flocculating binder; c) heat treatment (baking) to harden the cohesive binder; d) optionally at least partially zeolitizing the aggregate binder; and e) Recovery and optional activation of the zeolitic adsorbent material that may be used in the context of the present invention, generally activation between 100°C and 550°C.

[0047] In the above method, step a) may be carried out one or more times before step b) and / or after steps c) and / or d).

[0048] A baking step is generally carried out preferably between steps b) and d), generally at a temperature of between 400° C. and 600° C., although this is by no means essential. Alternatively, if a baking step is carried out, it may be possible to carry out step a) after this baking step and before step d), regardless of whether step a) has already been carried out before step b).

[0049] According to a preferred embodiment of the method for preparing a zeolitic adsorbent material that can be used in the method of the present invention, the step of forming the aggregate material into a shape is carried out according to any method known to those skilled in the art. This step of forming into a shape may be carried out during or after the aggregation step b) and may be followed by one or more cation exchange and / or impregnation steps a).

[0050] The heat treatment step described in the above method must not result in significant sintering of the metal atoms, which must remain as dispersed as possible in the zeolite. This can be easily observed by scanning electron microscopy (SEM) or transmission electron microscopy (TEM). Sintering of the metal atoms is easily avoided, in particular, by careful and strict control of the heat treatment temperature and time, as is well known.

[0051] Such methods for preparing zeolitic adsorbent materials exchanged and / or impregnated with one or more metals are well known to those skilled in the art, and reference may be made, for example, in a non-limiting manner, to EP 1 125 635 or to the document "Metal Sites in Zeolites: Synthesis, Characterization and Catalysis", Q. Zhang et al., Chem. Rev. (2023), 123(9), 6039-6106, for a precise description of how zeolitic adsorbent materials that can be used in the context of the method of the present invention are prepared.

[0052] More particularly, cation exchange can be carried out according to any method known to those skilled in the art, for example, by contacting the zeolitic adsorbent material with one or more, preferably aqueous, salt solutions, at least one of which contains one or more metal salts. The cation exchanges can be single or multiple, and if multiple, successive exchanges can be with the same or different salt solutions, each exchange step being preceded and / or followed by at least one washing and / or heat treatment step, the heat treatment being optionally an oxidizing or reducing treatment.

[0053] The impregnation operation, whether wet or dry impregnation, can also be easily carried out according to any method known to those skilled in the art. The term "wet impregnation" refers to placing the zeolitic adsorbent material in aqueous and / or organic suspension in contact with one or more, preferably aqueous, salt solutions, at least one of which contains one or more metal salts, the wet impregnation operation optionally preceded and / or followed by at least one heat treatment step, which is optionally an oxidation or reduction treatment. The term "dry impregnation" refers to contacting the zeolitic adsorbent material with a precise volume of one or more, preferably aqueous, salt solutions, at least one of which contains one or more metal salts, the dry impregnation operation optionally preceded and / or followed by at least one heat treatment step, which is optionally an oxidation or reduction treatment.

[0054] The various steps listed above, cation exchange and / or impregnation, may be carried out one or more times or may be combined, for example a cation exchange operation followed by a wet or dry impregnation operation, a washing step after the cation exchange, and optionally a heat treatment before the impregnation operation.

[0055] These different cation exchange and impregnation operations result in the presence of at least one metal in the form of a cation in the zeolitic adsorbent material. Prior to use in the process of the invention, and if necessary or desirable, treatment with a reducing element, for example advantageously under a stream of hydrogen gas, makes it possible to reduce the valence of the metal, possibly down to a valence of zero.

[0056] Non-limiting examples of zeolite-based adsorbent materials that can be used in the process of the present invention are as follows:

[0057] a sodium MFI (MFI-Na) type zeolite or a protonated MFI (MFI-H) zeolite having a Si / Al molar ratio of 2 to 20, and a content of at least one metal selected from Pd, Pt, Ni, Ti, Co, Zn, Ce, Fe, Cu, Zn and Ag of 0.1% to 9%, preferably at least copper, and optionally at least one other metal selected from Pd, Pt, Ni, Ti, Co, Zn, Ce, Fe, Zn and Ag, preferably selected from Pd, Pt and Ni; sodium FAU (FAU-Na) zeolite or protonated FAU (FAU-H) zeolite with a Si / Al molar ratio of 1.25 to 20, with a content of 0.1% to 9% of at least one metal selected from Pd, Pt, Ni, Ti, Co, Zn, Ce, Fe, Cu, Zn and Ag, preferably at least copper, and optionally at least one other metal selected from Pd, Pt, Ni, Ti, Co, Zn, Ce, Fe, Zn and Ag, preferably selected from Pd, Pt and Ni, a sodium LTA (LTA-Na) zeolite or a protonated LTA (LTA-H) zeolite with a Si / Al molar ratio equal to 1, with a content of at least one metal selected from Pd, Pt, Ni, Ti, Co, Zn, Ce, Fe, Cu, Zn and Ag, preferably at least copper, and optionally at least one other metal selected from Pd, Pt, Ni, Ti, Co, Zn, Ce, Fe, Zn and Ag, preferably selected from Pd, Pt and Ni, and RHO-sodium (RHO-Na) zeolite or protonated RHO (RHO-H) zeolite with a Si / Al molar ratio of 1 to 20, with a content of 0.1% to 9% of at least one metal selected from Pd, Pt, Ni, Ti, Co, Zn, Ce, Fe, Cu, Zn and Ag, preferably at least copper, and optionally at least one other metal selected from Pd, Pt, Ni, Ti, Co, Zn, Ce, Fe, Zn and Ag, preferably Pd, Pt and Ni.

[0058] According to a preferred embodiment, the zeolitic adsorbent material used in the present invention is a particulate material comprising at least one zeolite exchanged or impregnated with copper and, optionally, one or more other metals selected from series 3 to 12 in zerovalent metallic form or in oxidized or reduced form.

[0059] A most particularly preferred embodiment of the process of the present invention uses a zeolitic adsorbent material which is a particulate material comprising at least one zeolite exchanged or impregnated with copper or with copper mixed or alloyed with one or more metals selected from palladium, platinum, iron, and zinc.

[0060] According to yet another preferred embodiment, the process of the present invention uses a zeolitic adsorbent material which is a particulate material comprising at least one faujasite (FAU) type zeolite, preferably an FAU type zeolite having a Si / Al ratio of 1 to 100, such as an FAU-X or FAU-Y type zeolite further comprising sodium and copper, or copper mixed or alloyed with one or more metals selected from palladium, platinum, iron, and zinc, the metals optionally being exchanged or impregnated with the zeolitic adsorbent material.

[0061] According to another preferred embodiment, the process of the present invention uses a zeolitic adsorbent material which is a particulate material comprising at least one faujasite (FAU) type zeolite, preferably an FAU type zeolite having a Si / Al ratio of 2 to 100, for example an FAU-Y type zeolite further comprising sodium and copper, or copper mixed or alloyed with one or more metals selected from palladium, platinum, iron, and zinc, the metals optionally being exchanged and / or impregnated with the zeolitic adsorbent material.

[0062] According to yet another preferred embodiment, the process of the present invention uses a zeolitic adsorbent material which is a particulate material comprising at least one MEI type zeolite, preferably an MFI type zeolite having a Si / Al ratio of 10 to 100, sodium, and further comprising copper or copper mixed or alloyed with one or more metals selected from palladium, platinum, iron, and zinc, the metals optionally being exchanged or impregnated with the zeolitic adsorbent material.

[0063] In preferred embodiments, examples of zeolite adsorbent materials that can be used in the process of the present invention are as follows:

[0064] Protonated FAU Protonated FAU zeolite with a Si / Al ratio between 2 and 10 and a copper content between 7% and 9% by weight, Protonated FAU zeolite with a Si / Al ratio between 2 and 10 and a copper content between 4% and 7% by weight, Protonated FAU zeolite with a Si / Al ratio of 2-10, a copper content of 2%-4%, and a palladium content of 0.1%-1%; protonated FAU zeolite with a Si / Al ratio between 2 and 10, a copper content between 0.5% and 2% by weight, and a palladium content between 0.1% and 1% by weight; Protonated FAU zeolite with a Si / Al ratio between 2 and 10, a copper content between 0.5% and 2% by weight, and a platinum content between 0.1% and 1% by weight; Protonated FAU zeolite with a Si / Al ratio between 2 and 10, a copper content between 0.5% and 2% by weight, and a nickel content between 0.1% and 5% by weight; Protonated FAU zeolite with a Si / Al ratio between 2 and 10, a copper content between 0.5% and 2% by weight, and an iron content between 0.1% and 5% by weight; protonated FAU zeolite with a Si / Al ratio between 2 and 10, a copper content between 0.5% and 2% by weight, and a cobalt content between 0.1% and 1% by weight; protonated FAU zeolite with a Si / Al ratio between 2 and 10, a copper content between 0.5% and 2% by weight, and a zinc content between 0.1% and 5% by weight; protonated FAU zeolite with a Si / Al ratio between 2 and 10, a copper content between 0.5% and 2% by weight, and a titanium content between 0.1% and 5% by weight; Sodium FAU Sodium FAU zeolite with a Si / Al ratio of 2 to 10 and a copper content of 7% to 9% by weight; Sodium FAU zeolite with a Si / Al ratio of 2 to 10 and a copper content of 4% to 7% by weight; Sodium FAU zeolite with a Si / Al ratio between 2 and 10, a copper content between 2% and 4% by weight, and a palladium content between 0.1% and 1% by weight; Sodium FAU zeolite with a Si / Al ratio between 2 and 10, a copper content between 0.5% and 2% by weight, and a palladium content between 0.1% and 1% by weight; Sodium FAU zeolite with a Si / Al ratio between 2 and 10, a copper content between 0.5% and 2% by weight, and a platinum content between 0.1% and 1% by weight; Sodium FAU zeolite with a Si / Al ratio between 2 and 10, a copper content between 0.5% and 2% by weight, and a nickel content between 0.1% and 5% by weight; Sodium FAU zeolite with a Si / Al ratio between 2 and 10, a copper content between 0.5% and 2% by weight, and an iron content between 0.1% and 5% by weight; Sodium FAU zeolite with a Si / Al ratio between 2 and 10, a copper content between 0.5% and 2% by weight, and a cobalt content between 0.1% and 1% by weight; Sodium FAU zeolite with a Si / Al ratio between 2 and 10, a copper content between 0.5% and 2% by weight, and a zinc content between 0.1% and 5% by weight; Sodium FAU zeolite with a Si / Al ratio between 2 and 10, a copper content between 0.5% and 2% by weight, and a titanium content between 0.1% and 5% by weight; Protonated MFI Protonated MFI zeolite with a Si / Al ratio of 10-20 and a copper content of 7%-9% by weight, Protonated MFI zeolite with a Si / Al ratio of 10-20 and a copper content of 4%-7% by weight, Protonated MFI zeolite with a Si / Al ratio of 10-20, a copper content of 2%-4% by weight, and a palladium content of 0.1%-1% by weight, Protonated MFI zeolite with a Si / Al ratio of 10-20, a copper content of 0.5%-2% by weight, and a palladium content of 0.1%-1% by weight, Protonated MFI zeolite with a Si / Al ratio of 10-20, a copper content of 0.5%-2% by weight, and a platinum content of 0.1%-1% by weight, protonated MFI zeolite with a Si / Al ratio of 10-20, a copper content of 0.5%-2% by weight, and a nickel content of 0.1%-5% by weight; protonated MFI zeolite with a Si / Al ratio of 10-20, a copper content of 0.5%-2% by weight, and an iron content of 0.1%-5% by weight; Protonated MFI zeolite with a Si / Al ratio of 10-20, a copper content of 0.5%-2% by weight, and a cobalt content of 0.1%-1% by weight, Protonated MFI zeolite with a Si / Al ratio of 10-20, a copper content of 0.5%-2% by weight, and a zinc content of 0.1%-5% by weight; protonated MFI zeolite with a Si / Al ratio of 10-20, a copper content of 0.5%-2% by weight, and a titanium content of 0.1%-5% by weight; Sodium MFI Sodium MFI zeolite with a Si / Al ratio of 10-20 and a copper content of 7%-9% by weight; Sodium MFI zeolite with a Si / Al ratio of 10-20 and a copper content of 4%-7% by weight, Sodium MFI zeolite with a Si / Al ratio of 10-20, a copper content of 2%-4% by weight, and a palladium content of 0.1%-1% by weight; Sodium MFI zeolite with a Si / Al ratio of 10-20, a copper content of 0.5%-2% by weight, and a palladium content of 0.1%-1% by weight; Sodium MFI zeolite with a Si / Al ratio of 10-20, a copper content of 0.5%-2% by weight, and a platinum content of 0.1%-1% by weight; Sodium MFI zeolite with 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; Sodium MFI zeolite with a Si / Al ratio of 10-20, a copper content of 0.5%-2% by weight, and an iron content of 0.1%-5% by weight; Sodium MFI zeolite with a Si / Al ratio of 10-20, a copper content of 0.5%-2% by weight, and a cobalt content of 0.1%-1% by weight; Sodium MFI zeolite with a Si / Al ratio of 10 to 20, a copper content of 0.5% to 2% by weight, and a zinc content of 0.1% to 5% by weight; · Sodium MFI-type olite with a Si / Al ratio of 10-20, a copper content of 0.5%-2% by weight, and a titanium content of 0.1%-5% by weight.

[0065] As previously mentioned, the present invention relates to a method for purifying a hydrogen stream, in particular an electrolytic hydrogen stream, containing oxygen and water as impurities to be removed, and optionally nitrogen, and optionally other impurities inherent in hydrogen synthesis processes, in particular electrolytic hydrogen synthesis processes.

[0066] As previously mentioned, the method of the present invention is an "all-in-one" hydrogen purification method by removing both oxygen and water present as impurities in a hydrogen stream, more particularly a hydrogen stream that includes or consists of electrolytic hydrogen.

[0067] The term "all-in-one" method means that passage over a zeolite adsorbent material allows for the simultaneous (i.e., concomitant) at least partial or even total removal (content below the detection threshold) of oxygen and water present in a hydrogen stream within the same temperature range. It is well known to those skilled in the art that zeolites must operate at high temperatures to remove oxygen, and that at high temperatures zeolites adsorb little or no water and tend to desorb water. Therefore, the "all-in-one" method of the present invention has the significant advantage of removing both oxygen and water, and possibly other impurities, from a hydrogen stream while eliminating the step of changing the temperature range, thus facilitating an industrial process in terms of time, energy consumption, and productivity. Therefore, the method of the present invention can be considered to allow the purification of a hydrogen stream without the supply of external energy, for example, without the supply of external heat.

[0068] The purification process of the present invention can therefore be carried out according to any method known to those skilled in the art of gas purification, more particularly by adsorption of impurities onto a zeolitic adsorbent material as defined above. For example, the adsorption process according to the present invention can be selected from pressure and / or temperature swing processes, typically PSA ("Pressure Swing Adsorption"), PVSA ("Pressure Vacuum Swing Adsorption", which relies on desorption at subatmospheric pressure), TSA ("Temperature Swing Adsorption"), PTSA ("Pressure Temperature Swing Adsorption"), PVTSA ("Pressure Vacuum Temperature Swing Adsorption", which relies on desorption at subatmospheric pressure).

[0069] The fluid to be purified (hydrogen to be purified) contains, as indicated above, mainly hydrogen, but also water, oxygen and possibly nitrogen. The water content is generally between 20 ppmv and 1.5 mol%, preferably between 50 ppmv and 1.5 mol%, more preferably between 100 ppmv and 1.5 mol%, advantageously between 200 ppmv and 1.5 mol%. The oxygen content of the stream is generally between 5 ppmv and 1 mol%, preferably between 5 ppmv and 5000 ppmv, more preferably between 5 ppmv and 3000 ppmv, even more preferably between 5 ppmv and 1000 ppmv. The nitrogen content is between 0 and 1 mol%, generally between 10 ppmv and 1 mol%.

[0070] The process according to the invention can be carried out according to any conventional gas separation method, for example by passing the gas through one or more columns (also called "adsorbers" or more simply "reactors") containing at least one bed of a zeolitic adsorbent material as just defined. According to one embodiment, the process of the invention is carried out using at least two adsorbers, via techniques well known to those skilled in the art, especially when working with continuous flow.

[0071] Thus, the fluid to be purified is generally contacted with the zeolitic adsorbent material at a pressure of from 0.5 MPa to 5 MPa, preferably from 0.9 MPa to 5 MPa, more preferably from 1.5 MPa to 5 MPa, and at a temperature of from 10°C to 100°C, preferably from 15°C to 90°C, advantageously from 20°C to 60°C, typically from 25°C to 55°C.

[0072] In a preferred embodiment, after the adsorption step, the bed of zeolitic adsorbent material is regenerated, i.e., desorbed either by reduced pressure and countercurrent discharge (PSA and VPSA processes) or by temperature reduction (TSA processes), optionally in combination with reduced pressure and countercurrent discharge (PVTSA processes).

[0073] For PSA and VPSA processes, the desorption pressure is generally between 0.1 MPa and 1 MPa on the one hand and between 500 Pa and 95 kPa on the other hand. As a general rule, for obvious reasons of ease of process implementation and energy savings, the desorption temperature is close to the adsorption temperature; in other words, deliberate temperature changes are generally not made.

[0074] According to yet another preferred embodiment of the invention, a purge step may be carried out at the end of the desorption step by countercurrent reintroduction of a portion of the purified gas, typically less than 20% of the stream produced by the adsorber.

[0075] It should be understood that the process of the present invention may also include one or more pressure equalization steps between any of the different adsorbers. Pressure equalization steps can be advantageously carried out between the adsorption and desorption steps according to techniques well known to those skilled in the art. The advantage of providing one or more pressure equalization steps is, in particular, to minimize hydrogen losses throughout the process.

[0076] According to yet another variant, it may also be envisaged to recycle the gas collected during desorption, as is customary in hydrogen PSA.

[0077] For TSA and PVTSA processes, a portion of the purified gas (typically less than 20% of the stream produced by the adsorber) is heated to a temperature between 40°C and 250°C and then injected countercurrently into the adsorber, possibly at reduced pressure relative to the adsorbed phase (PVTSA), i.e., 1 kPa to 3 MPa. As with PSA and VPSA, different pressure equalization and purge configurations can be envisaged.

[0078] In the method of the present invention, the adsorption and desorption phases cyclically follow each other. The method may optionally include a cooling system integrated into the adsorber to avoid or at least minimize excessive heating of the adsorbent bed, which, as indicated above, inhibits water adsorption by the particulate zeolitic adsorbent material. The method may also include the step of drying the gas stream before and / or after passing it over the zeolitic adsorbent material containing at least one metal according to the present invention.

[0079] The fact that it is possible to dry, i.e. to adsorb the water present or formed in the same material, allows the simplification of the processes downstream of the electrolyzer while producing hydrogen of the required quality. By implementing the method of the invention, a DEOXO unit is no longer specifically required.

[0080] The method of the present invention thus has many advantages, most particularly its ability to both reduce the dissolved oxygen in a hydrogen stream and adsorb any water already present in the hydrogen stream, as well as water formed by the reduction of dissolved oxygen. The method of the present invention therefore makes it easy to obtain, on an industrial scale, hydrogen streams, particularly electrolytic hydrogen streams, containing less than 5 ppmv of oxygen and less than 1 ppmv of water, more particularly hydrogen streams having a purity greater than 99.97% by volume, even more particularly greater than 99.98%, and even better still greater than 99.99% by volume. These percentages are calculated from measurements of the amount of residual impurities. The amount of impurities is determined using an ionization mass spectrometer as follows:

[0081] According to another aspect of the present invention, the invention relates to the purified hydrogen stream obtained according to the aforementioned method and its use as a fuel in the electrical and electronic fields, in particular as an industrial reagent in fuel cells, but also to supply Liquid Organic Hydrogen Carrier (LOHC) cycles such as toluene (methylcyclohexane) or other aromatic hydrocarbons, for example benzyltoluene or dibenzyltoluene (see, for example, International Patent Applications WO 2014 / 082801 and WO 2021 / 176170), for known applications, more generally for synthesis in the chemical, pharmaceutical and petrochemical industries, to name just a few.

[0082] According to another aspect, the present invention relates to the use of a zeolitic adsorbent material as defined above for the purification of hydrogen streams, in particular for the purification of electrolytic hydrogen.

[0083] According to yet another aspect, the present invention relates to a method for preparing high purity hydrogen, comprising at least the following steps:

[0084] 1) electrolysis of an aqueous solution containing primarily hydrogen oxide to produce a hydrogen stream and an oxygen stream; 2) Recovery of the hydrogen stream from the electrolysis step 1); 3) Purifying the hydrogen stream recovered in step 2) by passing it over a zeolitic adsorbent material, as defined above; and 4) Recovery of high-purity hydrogen.

[0085] It is to be understood that the method for preparing high purity hydrogen according to the present invention comprises an electrolysis step 1) which can be carried out in a conventional manner well known to those skilled in the art.

[0086] This method therefore allows the production of very high purity hydrogen in an efficient and economical manner, in particular more economically than the synthetic methods known today for preparing hydrogen by electrolysis of water.

[0087] analysis technology Si / Al molar ratio and degree of exchange The determination of the Si / Al molar ratio and the degree of exchange is carried out by any chemical analysis technique known to those skilled in the art, among which mention may be made of the technique of chemical analysis by X-ray fluorescence as described in standard NF EN ISO 12677:2011 on a wavelength dispersive spectrometer (WDXRF), for example a Bruker Tiger S8 machine.

[0088] X-ray fluorescence is a spectral technique that utilizes the photoluminescence of atoms in the X-ray range to establish the elemental composition of a sample. Excitation of atoms, typically by an X-ray beam or electron bombardment, produces specific radiation after the atoms return to their ground state. X-ray fluorescence spectroscopy has the advantage of being largely independent of the chemical elemental combination, resulting in accurate determinations, both quantitatively and qualitatively. After calibration for each oxide, measurement uncertainties of less than 0.4% by weight are typically obtained.

[0089] These elemental chemical analyses make it possible to ascertain the Si / Al molar ratio of the starting zeolite, the content of deposited metals, and the quality of the ion exchange. In the present description, the uncertainty in the measurement of the Si / Al molar ratio is ±5%. The quality of the ion exchange is related to the number of moles of sodium oxide NaO remaining in the agglomerated zeolitic adsorbent after the exchange. It should be noted that the contents of the various oxides are given as weight percentages relative to the total weight of the anhydrous zeolitic adsorbent material.

[0090] The Si / Al molar ratio of the zeolite present in the zeolitic adsorbent material is measured by solid-state silicon nuclear magnetic resonance (NMR) spectroscopy. For purposes of this invention, the uncertainty in the measurement of the Si / Al molar ratio is ±5%.

[0091] metal content The amount of metal present in the zeolitic adsorbent material is also obtained from X-ray fluorescence analysis as described above and is expressed as mass percentage of metal.

[0092] Metal particle size The number average diameter of the metal particles contained in the zeolite-based adsorbent material is estimated by observation using a scanning electron microscope (SEM).

[0093] 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 diameters of at least 200 particles are then measured using dedicated software, such as the Smile View software published by LoGraMi. The accuracy is on the order of 3%. The measurement of a histogram formed from the diameter measurements simultaneously allows the determination of the standard deviation σ of the distribution.

[0094] Zeolite adsorbent particle size The volume mean diameter of the zeolite adsorbent is determined by analysis of the particle size of the aggregate sample by imaging according to ISO standard 13322-2:2006 using a conveyor belt to pass the sample in front of a camera objective.

[0095] The volume mean diameter is then calculated from the particle size by applying ISO standard 9276-2:2001. In this specification, the term "volume mean diameter" or "size" is used for zeolitic aggregates. The accuracy is about 0.01 mm for the size range of the aggregates of the present invention.

[0096] Qualitative analysis by X-ray diffraction The purity of the zeolite in the zeolitic adsorbent material is assessed by X-ray diffraction analysis, known to those skilled in the art by the acronym XRD. This determination is carried out on a Bruker brand XRD instrument.

[0097] This analysis allows differentiation of the various zeolites present in the adsorbent material, as each zeolite structure has a unique diffraction pattern defined by the positions and relative intensities of the diffraction peaks.

[0098] Before measurement, the zeolitic material is crushed and then spread and smoothed onto the sample holder by simple mechanical compression.

[0099] The conditions for acquiring the diffraction patterns on a Bruker D5000 machine are as follows:

[0100] Cu tube used at 40kV-30mA Slit size (divergence slit, scattering slit, and analysis slit) = 0.6 mm Filter: Ni Sample device rotation: 15 rpm Measurement range: 3°<2θ<50° Step: 0.02° Time count per step: 2 seconds.

[0101] The obtained diffraction patterns are interpreted using EVA software with the identification of the zeolite, aided by the ICDD PDF-2 database, 2011 release.

[0102] Microcrystallinity by Dubinin volume Dubinin volume (or micropore volume V mi ) is determined by conventional methods well known to those skilled in the art, in particular by measuring the adsorption isotherms of gases such as nitrogen, argon, oxygen, etc., at liquefaction temperatures. Nitrogen is preferably used. Prior to the adsorption measurements, the zeolite crystals of the invention are subjected to vacuum (pressure <6.7 x 10 -4 The adsorption isotherm is measured at 77 K (200 psi) at 300°C to 450°C for a period ranging from 9 to 16 hours. For example, for MFI or FAU zeolites, the nitrogen adsorption isotherm at 77 K is measured with a Micromeritics ASAP 2020 instrument, taking at least 35 measurement points at relative pressures with a P / P ratio between 0.002 and 1. The micropore volume is determined from the resulting isotherm according to the Dubinin-Raduskevitch equation by applying ISO standard 15901-3:2007. The micropore volume thus evaluated is expressed as cm of liquid adsorbent per gram of anhydrous adsorbent. 3 The measurement uncertainty is ±0.003 cm 3 .g -1 is. [Example]

[0103] The hydrogen stream is withdrawn from the electrolyzer at a temperature of 50° C. The hydrogen stream is pressurized to 0.8 MPa. The hydrogen stream contains 3000 ppmv oxygen and 1000 ppmv water.

[0104] The electrolytic hydrogen stream to be purified is introduced into a column containing 1 liter of zeolitic adsorbent material. The contact time between the stream and the zeolitic adsorbent material is set to 10 seconds. The zeolitic adsorbent material is formed from 1 mm diameter beads obtained by agglomerating H-MFI (protonated MFI) zeolite crystals with a Si / Al ratio equal to 12.5, a copper content of 4% by weight, and a palladium content of 0.2% by weight with 20% by weight of a binder.

[0105] The purified hydrogen stream recovered at the column outlet is analyzed using an ionization mass spectrometer. The oxygen content is determined by measurement using a GMACX galvanic cell, and the residual water content is determined using a Panametrics humidity probe. The hydrogen thus purified contains 2 ppmv oxygen and 0.3 ppmv water.

Claims

1. 1. A method for purifying a hydrogen stream containing water, oxygen, and optionally nitrogen, comprising: - at least one step of contacting the hydrogen stream to be purified with a zeolitic adsorbent material comprising at least one metal from columns 3 to 12 of the periodic table of the elements in zero-valent metallic form or in oxidized or reduced form; and - recovery of at least one purified hydrogen stream; A method comprising:

2. 10. The method of claim 1, wherein the hydrogen being purified comprises electrolytic hydrogen.

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

4. 4. The method according to any one of claims 1 to 3, wherein the at least one metal is selected from the metals of columns 3 to 12 of the Periodic Table of the Elements, including the lanthanides and actinides, preferably from iron, cobalt, cerium, nickel, titanium, copper, zinc, palladium, silver and platinum, either alone or as a mixture of two or more thereof.

5. 5. A method according to any one of claims 1 to 4, wherein the zeolitic adsorbent material comprises at least one zeolite selected from LTA, FAU, RHO and MFI zeolites and mixtures of two or more thereof, preferably selected from FAU-type zeolites, MFI-type zeolites and mixtures thereof in all proportions and at all Si / Al ratios.

6. 6. The method of any one of claims 1 to 5, wherein the zeolitic adsorbent material is a particulate material comprising at least one zeolite exchanged or impregnated with copper and, optionally, one or more other metals selected from series 3 to 12 in zerovalent metallic form or in oxidized or reduced form.

7. 7. A process according to any one of claims 1 to 6, wherein the hydrogen stream to be purified is contacted with the zeolitic adsorbent material at a pressure of from 0.5 MPa to 5 MPa, preferably from 0.9 MPa to 5 MPa, more preferably from 1.5 MPa to 5 MPa, and at a temperature of from 10°C to 100°C, preferably from 15°C to 90°C, advantageously from 20°C to 60°C, typically from 25°C to 55°C.

8. 1. Use of a zeolitic adsorbent material comprising at least one metal selected from metals of columns 3 to 12 of the periodic table of the elements, including the lanthanides and actinides, preferably at least one metal selected from iron, cobalt, cerium, nickel, titanium, copper, zinc, palladium, silver and platinum, either alone or as a mixture of two or more thereof, for the purification of hydrogen streams, in particular for the purification of electrolytic hydrogen.

9. Use of the purified hydrogen stream obtained by the method according to any one of claims 1 to 7 as a fuel, as an industrial reagent, in the electrical and electronics field, in fuel cells, for supplying liquid organic hydrogen carrier (LOHC) cycles, and for synthesis in the chemical, pharmaceutical and petrochemical industries.

10. 1. A method for preparing high purity hydrogen, comprising at least the following steps: 1) electrolysis of an aqueous solution containing primarily hydrogen oxide to produce a hydrogen stream and an oxygen stream; 2) recovery of said hydrogen stream from electrolysis step 1); 3) Purification of the hydrogen stream recovered in step 2) by the method of any one of claims 1 to 7, and 4) Recovery of high-purity hydrogen.

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