WO2017025685A1

WO2017025685A1 - Process for trapping oxygen

Info

Publication number: WO2017025685A1
Application number: PCT/FR2016/052050
Authority: WO
Inventors: Jérôme Delmas; Philippe Capron; Isabelle Rougeaux
Original assignee: Commissariat A L'energie Atomique Et Aux Energies Alternatives; Intelligent Energy Ltd.
Priority date: 2015-08-13
Filing date: 2016-08-08
Publication date: 2017-02-16
Also published as: FR3040002A1

Abstract

The present invention relates to a process for trapping oxygen according to which gaseous oxygen is brought into contact with an anion exchanger support, said anion exchanger support comprising fixed cationic groups and free anions X^-, X^- being an anion selected from the group comprising SO₃ ^2-; S₂O₅ ^2-; S₂O₇ ^2-, NO₂ ^-; and mixtures thereof.

Description

PROCESS FOR TRAPPING OXYGEN

FIELD OF THE INVENTION The present invention relates to a method for trapping oxygen in the form of gas through the use of an anion exchange medium. It also relates to the device for implementing this method.

The field of use of the present invention relates to any application requiring the elimination of gaseous oxygen, in particular hydrogen generators.

PRIOR STATE OF THE TECHNIQUE

Many applications require anaerobic conditions, especially to prevent corrosion of iron or cobalt materials. For this, various technologies have been developed to remove oxygen, whether it is dissolved in a solution or it is in the form of gas.

By way of example, document CA 2 233 420 describes a method for limiting corrosion in a boiler by using sulphite ions in the boiler water.

US 4,231,869 discloses a process wherein a cobalt catalyst accelerates the reaction between solution dissolved oxygen and sulfite ions to form sulfate ions.

These solutions may be satisfactory in liquid media; however, some applications require the removal of gaseous oxygen. This is particularly the case of the generation of hydrogen from the catalyzed hydrolysis of a solution based on chemical hydride (more exactly based on borohydride) in a hydrogen generator, as described in the documents WO 2010/051557 and WO 2012/003112.

During the storage of the hydrogen generator, before its operation, it is essential to remove the oxygen present in order to maintain the performance of the catalyst by preventing its oxidation. For this, the hydrogen generator is generally purged before being packaged in a sealed package. However, it is possible for oxygen to enter the interior of the hydrogen generator during its operation, in particular by permeation through the materials constituting the generator. It can be an amount of oxygen of the order of 1 μΐ per day to 5 ml per day.

In order to remedy this problem, gaseous oxygen absorbers have been developed to be positioned in the hydrogen generator. These include iron-based compounds, for example iron oxides, iron 0 or iron boride (FeB _x ).

To be effective, these absorbers generally require the presence of water or must be in the form of nanoparticles. Their use or preparation is therefore restrictive. The present invention solves this technical problem by trapping oxygen gas without the need for water and without using nanoparticles.

SUMMARY OF THE INVENTION The Applicant has developed a new process for trapping gaseous oxygen through the use of an anion exchange support (polymer or inorganic support). The entrapment of gaseous oxygen may be carried out in the presence or absence of water.

Ion exchange polymers (anions or cations) are commonly referred to as ion exchange resins. These are polymers capable of exchanging ions (anions or cations). This type of polymer is used in the present invention to trap oxygen gas.

More specifically, the present invention relates to an oxygen scavenging method according to which gaseous oxygen is brought into contact with an anion exchange support, said anion exchange support comprising fixed cationic groups and free anions X ^". Where X ^" is an anion selected from the group consisting of SO ₃ ^2" , S ² O ₅ ^{2 "} , S ² O 7 ^2" , NO ² ^" , and mixtures thereof. One of the main advantages of the present invention resides in the trapping of gaseous oxygen by means of an anion exchanger carrier in solid form. Unlike the processes of the prior art using sulphite ions free SO ₃ ^{2 "} , the oxygen scavenging is advantageously carried out in the absence of a catalyst or a solvent such as water, however, according to a particular embodiment, a transition metal catalyst may be used, for example a cobalt salt.

The present invention can be implemented in any type of application that requires trapping gaseous oxygen.

Thus, another subject of the invention relates to a process for trapping gaseous oxygen in a hydrogen generator, comprising the following steps:

placing in at least one hydrogen generator, at least one anion exchange support comprising fixed cationic groups and free anions X ^" , X ^" being an anion chosen from the group comprising SO3 ^{2 "} , S2O5 ^2" , S2O7 ^{2 ";} N0 ₂ ^~ , and mixtures thereof;

oxygen is trapped by contacting the oxygen gas with the anion exchange medium;

hydrogen is generated.

Oxygen can also be trapped after the generation of hydrogen, in particular by contacting the gases (H ₂ and O ₂ ) with the anion exchange support.

The present invention can be implemented in any type of application which requires trapping gaseous oxygen and the elimination of any basic and / or anionic and / or cationic impurities.

Thus, another subject of the invention relates to a process for trapping gaseous oxygen and for purifying hydrogen in a hydrogen generator, comprising the following steps:

placing in an hydrogen generator an ion exchange support comprising:

^■ at least one anion exchange medium comprising fixed cationic groups and free anions X ^", ^X" is an anion selected from the group consisting of SO 3 ^{2 ",} ^{2 S2O5"} S2O7 ^{2 ",} N0 _^2", and mixtures thereof ; and

^■ at least one cation exchange carrier comprising free cations C _t ^+; oxygen is trapped by contacting the oxygen gas with the ion exchange support;

hydrogen is generated; the hydrogen is purified by contacting the generated hydrogen with the ion exchange support.

Free anions X ^"of anion exchange medium react with oxygen gas to form ions SO ₄ ^2" (for SO ₃ ² anions), S ₂ 0 ₆ ^{2 ~} ions (for anions S2O5 ^{2 ")} , S ₂ 08 ² ions ^"(for ² S2O7 ^anions") and NO3 ions ^"(for anions N0 _2).

In general, any type of anion or cation exchange medium can be used in the present invention from the moment when these supports respectively have free anions X ^" (SO 3 ^2" , S ₂ 0 ₅ ^{2 "} , S ₂ 0y ^{2 "} , N0 ₂ ^" , and mixtures thereof) and free cations C _t ⁺ .

The anion exchange support may be a polymeric support or a mineral support such as, for example, zeolites or grafted silicas.

Advantageously, the anion exchange support is a polymer of at least one monomer chosen from the group comprising styrene; divinylbenzene; acrylic; and their mixtures.

Acrylic polymers include polymers synthesized from acrylates, methacrylates or acrylonitrile. They are generally crosslinked by divinylbenzene in the presence of a radical initiator according to conventional techniques forming part of the knowledge of those skilled in the art.

The monomers and other starting substances may preferentially be chosen from the following list:

monomers: styrenic or acrylic (styrene, acrylates, methacrylates, acrylonitrile);

crosslinking agent: divinylbenzene;

activation catalysts: azobisisobutyronitrile (AIBN), peroxides;

agents for chloromethylation: chloromethyl methyl ether CELCIOCH3 in the presence of a catalyst AICI3OU SnC - The anion exchange support may in particular be a polymer support chosen from the group comprising:

polymers with quaternary amine groups of the polymer-NR ₃ ⁺ / X ^" and / or N-polymer (ROH) (R ') ₂ ⁺ / X ^"type;

polymers with tertiary amine groups of the polymer-NHR ₂ ⁺ / X ^"type ;

polymers with secondary and / or primary amine groups of the polymer-NH ₂ R ⁺ / X ^" and / or polymer-NH ₃ ⁺ / X ^"type;

polymers containing sulfonium groups of the polymer-SR ₂ ⁺ / X ^"type ;

R and R 'being defined above as alkyl groups or aryl groups. The groups R and R 'are advantageously a CH ₃ group.

The anion exchange medium can in particular be a copolymer of styrene and divinylbenzene or a copolymer of acrylic and divinylbenzene. Divinylbenzene then plays the role of crosslinking agent. The anion-exchange polymer support may especially correspond to the functionalized copolymer (free anions X ^" ) of styrene and divinylbenzene corresponding to the CAS number 60177-39-1.

As already indicated, the anion exchange support comprises fixed cationic groups.

The cationic fixed groups of the anion exchange support are advantageously groups chosen from the group comprising: -NH ₃ ⁺ ; -NR ₃ ⁺ ; -NHR ₂ ⁺ ; -NH ₂ R ⁺ ; -N (ROH) (R ') ₂ ⁺ ; and -SR ₂ ⁺ ; R and R 'being alkyl or aryl. The groups R and R 'are advantageously a CH ₃ group.

The present invention can also implement a cation exchange support comprising free cations C _t ⁺ . These free cations C _t ⁺ are advantageously chosen from the group comprising Na ⁺ ions; H ⁺ ; K ⁺ ; and their mixtures. Advantageously, the cation exchange medium comprising free cations C _t ⁺ comprises fixed anions may be selected from -S0 ₃ ^"-H ₂ P0 ₄ ^~; COO -, and - CH ₂ -COO \

The cation exchange support may be a polymer of at least one monomer selected from the group consisting of styrene; divinylbenzene; acrylic; and their mixtures. It may especially be a cation exchange support selected from the group comprising:

polymers with sulphonic groups of polymer type -SO ₃ ^" / C _t ⁺ ;

polymers with phosphorus groups of polymer type -H ₂ PO 4 ^_ / C _t ⁺ ;

polymers with carboxylic groups of the polymer-C007 C _t ^{+ type} ;

polymers with carboxymethyl groups of the polymer-CH ₂ -COO ^" / C _t ^{+ type} .

According to a particular embodiment, a mixture of at least one anion exchange support and at least one cation exchange support can be used. In this case, the oxygen and any impurities from the generation of hydrogen can be simultaneously trapped. This mixture may especially correspond to the functionalized copolymer (free anions X ^" , free cations C _t ) of styrene and divinylbenzene corresponding to the CAS number 79956-14-2.The preparation of the anion-exchange or cation-exchange supports implemented in the The invention is carried out according to conventional techniques forming part of the general knowledge of those skilled in the art.

By way of example, an anion exchange support can be functionalized with S0 ₃ ^{2 "} anions by passing an S0 ₃ ^2" ion-based solution, for example an aqueous solution of Na ₂ SO ₃ or KHSO3. Exchange between the anions of the anion exchange carrier, for example OH ^" ions, and sulfite ions S0 ₃ ^2" is carried out. The sulphite ions then functionalize the anion exchange support. The number of effectively functionalized sites can be optimized by carrying out several passages of an X ^" anion solution or C _t ⁺ cations, or by adjusting the concentration.

Partial functionalization may be advantageous when the anion exchange carrier is also used to trap impurities resulting from the hydrogen generation reaction. Thus, an anion exchange support comprising both free anions X ^" and free anions OH ^" can fulfill this dual role of oxygen scavenger gaseous and impurities. Advantageously, the ion exchange support (anions or cations) has an exchange capacity of between 0.8 eq / L and 4.5 eq / L, more advantageously between 4 and 4.5 eq / L (1 eq / l). L = 1 equivalent per liter of ion exchange support). The exchange capacity makes it possible to express the number of sites of the polymer that can exchange charges. An equivalent corresponds to one mole of +1 or -1 charge ions or half a mole of +2 or -2 charge ions. The greater the exchange capacity, the more ion exchange medium comprises of ions that can be substituted, and the greater the amount of oxygen or impurities that can be trapped.

As already indicated, according to a particular embodiment, the anion exchange medium may be a mixture of anion exchange support and cation exchange support. In addition to the X ^" anions, the anion exchange support can thus comprise free anions OH ^" , Cl ^" , S0 ₄ ^{2 ~} , HC0 ₃ ^~ and / or free Na ⁺ , H ⁺ , K ⁺ cations.

The simultaneous presence of anion and cation exchange groups makes it possible: to absorb oxygen, for example by oxidation of free ions S0 ₃ ^{2 ~} to S0 ₄ ^{2 ~} ; to filter the impurities that may result from the generation of hydrogen, for example. As already indicated, it may be impurities NaB0 ₂ or NaOH resulting from the hydrolysis reaction of NaBH ₄ . Indeed, in a hydrogen generator, the hydrogen can be advantageously generated by hydrolysis of a borohydride, more advantageously by hydrolysis of the borohydride NaBH ₄ according to the following reaction:

NaBH ₄ + (2 + x) H ₂ 0 -> 4 H ₂ + NaB0 ₂ .xH ₂ 0 This reaction is generally facilitated by the presence of a catalyst, the activity of which is maintained by preventing its oxidation, by trapping oxygen according to the invention.

In general, in a process according to the invention, the anion exchange support is kept out of any solution in order to avoid any exchange between the free anions X ^" used to trap oxygen and anions present in solution, for example, the BH ₄ ^" or B0 ₂ ^" anions Furthermore, the presence of the ion exchange support (anions and / or cations) in solution would not allow the hydrogen generated to be purified The present invention also relates to a device comprising the free anion exchanger support X ^" for the purpose of trapping gaseous oxygen. More specifically, the device for trapping gaseous oxygen according to the invention comprises an anion exchange support, said anion exchange support comprising fixed cationic groups and free anions X ^" , X ^" being an anion chosen from the group comprising S0 ₃ ^{2 ~} ; S2O5 ^{2 "} ; S2O7 ^2" , N0 ₂ ^~ ; and their mixtures.

This device can be integrated into a hydrogen generator. Thus, the hydrogen generated can in particular be purified by eliminating the possible oxygen gas present, by passing through the device according to the invention. The invention and the advantages thereof will become more apparent from the following figures and examples given in order to illustrate the invention and not in a limiting manner.

DESCRIPTION OF THE FIGURES Figure 1 illustrates a conventional hydrogen generator.

FIG. 2 illustrates the method of functionalization of S0 ₃ ² anions on an ion exchange support and the absorption of oxygen on this ion exchange support.

Figures 3 and 4 illustrate the method according to the invention for trapping gaseous oxygen present in a hydrogen generator.

FIG. 5 illustrates the evolution of the pressure of the hydrogen generator as a function of time in the presence of an ion exchange support according to the invention (functionalized

S0 ₃ ^{2 "} ) or solid Na ₂ SO ₃ .

FIG. 6 illustrates the evolution of the volume of oxygen absorbed as a function of time in the presence of an ion exchange support according to the invention (functionalized S0 ₃ ^{2 ~} ) or of solid Na ₂ SO ₃ .

Figure 7 shows a device comprising a hydrogen generator and a condensate collector from the hydrogen generator.

FIG. 8 illustrates the partial functionalization of an anion and cation exchange support with S0 ₃ ^{2 "} and Na ⁺ ions.

Figure 9 illustrates the entrapment of oxygen and the purification of hydrogen according to the invention.

Figure 10 shows the evolution of the pressure of the hydrogen generator as a function of time in the presence of an ion exchange carrier (functionalized S0 ₃ ^{2 ")} according to the invention.

FIG. 11 represents the pH of the condensates coming from the generator during the hydrolysis of NaBH ₄ according to one embodiment of the invention and according to a counterexample. DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 represents a conventional hydrogen generator (1) comprising: a reaction medium (2) making it possible to generate hydrogen, in particular by hydrolysis of borohydride;

a catalyst (3);

a chamber (4) providing the interface between the reaction medium (2) and the outlet valve (6) of the generated hydrogen;

a membrane (5) porous to gases (hydrogen and oxygen) and preferably liquid impermeable for the entry of hydrogen into the chamber (4).

FIG. 2 illustrates the functionalization of an ion exchange support by exchange of free OH ^" anions with free anions X ^" = SO ₃ ^{2 "} . Once the functionalization is carried out at least partially, the support can be used in the context of of the present invention according to the oxygen scavenging step also illustrated in Figure 2. The fixed cations of this support are ammonium-NR ₃ ⁺ .

The ion exchange support (7) can be positioned in any location of the hydrogen generator (1). However, and advantageously, it is not totally immersed in the reaction medium (2), so as to avoid any rapid exchange between the free anions X ^" of the ion exchange medium (7) and for example the ionic ions. type BH ₄ ^" that can understand the reaction medium (2).

According to a preferred embodiment of the invention, the ion exchange support (7) (anions and optionally cations) is advantageously positioned in the chamber (4) (FIG. 3). Thus, it makes it possible to trap the oxygen gas present in the hydrogen generator and thus prevents the aging of the catalyst (3) by oxidation (FIG. 4). The oxygen scavenging is therefore advantageously carried out before the start of hydrogen generation. However, the present invention allows for the continuous entrapment of gaseous oxygen during the generation of hydrogen.

Once the hydrogen is generated, it is removed from the hydrogen generator (1) by the valve (6) after being brought into contact with the ion exchange medium (7). Optionally, the hydrogen can then be purified by passing through a device (8) allowing the condensation of any impurities, and by passing through a filter (9) (Figure 7). As already indicated, the main role of the ion exchange support (7) is to trap the oxygen gas by means of the free anions X ^" .

According to a particular embodiment, the ion exchange support (7) can trap the oxygen gas by means of the free anions X ^" and any impurities resulting from the generation of hydrogen. Ions (7) can be the mixture of an anion exchange support comprising free anions X ^" and a cation exchange support comprising free cations C _t ⁺ . FIG. 8 represents the partial functionalization of a mixture containing:

an anion exchange support having fixed groups -NR ₃ ⁺ and free anions OH ^" ;

a cation exchange support having fixed groups -SO ₃ ^" and free cations H ⁺ .

According to the particular embodiment illustrated in FIG. 8, the simultaneous functionalization of these two supports is carried out by exchange with a solution of Na ₂ SO ₃ .

At the end of the partial functionalization, the free anions S0 ₃ ^{2 "} and OH ^{" as} well as the free Na ⁺ and H ⁺ cations can trap oxygen gas and any X ⁺ and anionic cationic impurities Y ^" (FIG. 9). .

Thus, a cation exchange support can be used to generate an acidic condensate, while a mixture of anion exchange media and cations can generate a condensate with a neutral pH, indicating that all the contaminants have been trapped by the support and the gaseous hydrogen is free or essentially free of contaminants

This hydrogen purification step can be very important especially when the hydrogen is intended to be used in a fuel cell.

EXAMPLES OF CARRYING OUT THE INVENTION

Two types of anion exchange carriers were functionalized with sulfite ions (INV-1 and INV-3) and compared with solid sodium sulfite (CE-1) or with a cation exchange support (CE-2). 1 / Comparison between an anion exchange support according to the invention and Na? SC

1.1 / Preparation of an anion exchange medium having sulphite ions according to the invention (INV-1)

A commercial anion exchange support (polymer referenced Amberjet 4200 from Dow Chemical) having the following properties has been functionalized:

spherical balls having a diameter of between 0.58 and 0.70 mm;

polymer matrix: copolymer of styrene and divinylbenzene;

fixed functional group: tertiary ammonium cation (trimethylammonium);

free ionic form: OH ^" ;

total exchange capacity of 1.2 eq / L.

It has been functionalized in the laboratory with sulphite ions.

The functionalization is carried out according to the following steps (FIG. 2):

4 g of a solution containing 5% by weight of Na ₂ SO ₃ (1.6 mmol) in distilled water was passed through 2.6 ml of carrier (Amberjet 4200 polymer from Dow Chemical);

the support (polymer) thus functionalized is dried under vacuum for 24 hours at room temperature.

The drying of the functionalized polymer with the anions SO ₃ ^{2 "} is not essential, but this step makes it possible to validate the oxygen scavenging tests by loss of pressure (FIG. It can not be dissolved in the polymeric support, since it is not moist, oxygen is necessarily trapped by reaction with the sulphite ions as shown in FIG.

Thus, the functionalized polymeric support is evaluated in the absence of any other compound.

It is possible to determine the exact amount of sulphite ions of the support thus functionalized, for example by measuring the difference in concentration of sulphite ions in the functionalization solution, that is to say by comparing the concentration of sulphite ions before and after the functionalization. Conventional techniques can be implemented, including iodometric or infrared spectroscopy titration. 1.2 / Evaluation of the anion exchange medium with sulphite ions according to the invention (INV-1) relative to solid sodium sulphite (CE-1)

Oxygen trapping is evaluated in a stainless steel device comprising a 5mL tank connected to a pressure sensor. The total volume is 71 mL (Figures 3 and 4).

2.6mL of functionalized polymer support (INV-1) are placed in the reservoir. A monitoring of the pressure inside the device is performed (Figure 5).

The same experiment (CE-1) is carried out by placing 200 mg of solid Na ₂ SO ₃ (0.0016 moles of S0 ₃ ^{2 ~} ) in the tank. 1.3 / Results for oxygen scavenging (INV-1, CE-1)

Depression is observed in the reservoir containing the functionalized polymer support according to the invention (INV-1). There was therefore oxygen uptake (Figure 6).

On the other hand, no variation of pressure is observed for the counter-example CE-1 (solid Na ₂ SO ₃ ). The trapping of oxygen therefore requires that the sulphite be in ionic form. The present invention makes it possible to have a support having fixed cations and free anions which make it possible to trap oxygen.

Trapping of oxygen and impurities: comparison between a mixture of anion and cation exchange carriers (INV-3) according to the invention and the absence of ion exchange support (CE-3) 2.1 / Preparation of a mixture of anion exchange media and cations according to the invention (INV-3)

An anion and cation exchange commercial support (polymer referenced Amberlite IRN 150 from Dow Chemical, CAS 79956-14-2) is functionalized with sulphite ions. This polymeric support has the following properties:

spherical balls having a diameter of between 0.58 and 0.70 mm;

polymer matrix: copolymer of styrene and divinylbenzene; fixed functional groups: tertiary ammonium cation (trimethylammonium) for the anion exchange polymer and SO ₃ ² anions for the cation exchange polymer;

free ion form: OH ^" for the anion exchange polymer and H ⁺ for the cation exchange polymer;

total exchange capacity of 1, 2 eq / L for the free anionic functions OH ^" and 1, 9 eq / L for the free cationic functions H ⁺ .

This ion exchange polymer support comprises 50% of free cationic functions H and 50% of free anionic functions OH ^" .

The functionalization is carried out according to the following steps:

5.5 ml of a solution containing 5% by weight of Na ₂ SO ₃ in distilled water was passed through 7.2 ml of the anion and cation exchange support;

drying of the ion exchange support under vacuum for 24 hours at room temperature.

Considering an exchange efficiency of 100%, 50% of the free anionic sites are exchanged with SO ₃ ^{2 -} ions, the ion exchange support is thus partially functionalized with the sulphite ions (FIG.

2.2 / Entrapment of oxygen (INV-3)

Oxygen trapping is evaluated in a stainless steel device comprising a 5mL tank connected to a pressure sensor (Figure 7). The total volume is 71mL.

1, 6 g of ion exchange support are placed in the tank (INV-3), more precisely in the chamber connected to the hydrogen outlet valve (FIG. 7). This generator corresponds to the device in 1.21 above.

A monitoring of the pressure inside the device is performed (Figure 10).

Depression is observed in the hydrogen generator, which demonstrates oxygen scavenging. 2.3 / Entrapment of impurities (INV-3, CE-3)

The hydrogen generator of item 2.2 / above is activated to generate hydrogen by hydrolysis of 10 g of NaBH ₄ . 160mg of ion exchange support are used.

Throughout the life of the hydrogen generator, the condensate from the generator is trapped and collected (Figure 7). Once the hydrogen generation is complete, a measurement of the pH of the condensate is carried out (FIG. 11).

A comparison is made with a generator containing no ion exchange support, the chamber connected to the hydrogen outlet valve being empty (CE-3). The pH of the condensate from the generator containing the partially functionalized ion exchange support (INV-3) is neutral while the pH of the condensate from the generator does not contain ion exchange support (CE-3) is basic (FIG. 11). The impurities resulting from the hydrolysis reaction of NaBH ₄ in the presence of the cobalt-based catalyst are trapped by the ion exchange support which fulfills the filter function.

Thus, this type of partially functionalized ion exchange support makes it possible to trap the oxygen present in the free volume and the ionic impurities resulting from the hydrolysis of NaBH ₄ .

Claims

An oxygen scavenging method in which gaseous oxygen is contacted with an anion exchange support, said anion exchange support comprising fixed cationic groups and free X ^" anions,

X ^" being an anion selected from the group consisting of S0 ₃ ^{2 ~} ; S ² O 5 ^2" ; S2O7 ^{2 "} , N0 ₂ ^~ and mixtures thereof.

Oxygen scavenging method according to claim 1, characterized in that the anion exchange medium has an exchange capacity of between 0.8 eq / L and 4.5 eq / L.

Oxygen scavenging method according to claim 1 or 2, characterized in that the anion exchange carrier is a polymeric carrier or a mineral carrier.

An oxygen scavenging method according to one of claims 1 to 3, characterized in that the fixed cationic groups of the anion exchange support are groups selected from the group consisting of:

-NH ₃ ⁺ ; -NR ₃ ⁺ ; -NHR ₂ ⁺ ; -NH ₂ R ⁺ ; -N (ROH) (R ') ₂ ⁺ ; and -SR ₂ ⁺ ; R and R 'being alkyl or aryl.

An oxygen scavenging method according to one of claims 1 to 4, characterized in that the anion exchange carrier is a polymeric carrier selected from the group consisting of:

polymers with tertiary amine groups of the polymer-NHR ₂ ⁺ / X ^"type ; polymers with secondary and / or primary amine groups of the polymer-NH ₂ R ⁺ / X ^" and / or polymer-NH ₃ ⁺ / X ^"type ;

polymers containing sulfonium groups of the polymer-SR ₂ ⁺ / X ^"type ;

R and R 'being alkyl or aryl.

An oxygen scavenging method according to one of claims 1 to 5, characterized in that the anion exchange carrier is a copolymer of styrene and divinylbenzene or a copolymer of acrylic and divinylbenzene. A process for trapping gaseous oxygen in a hydrogen generator, comprising the steps of:

at least one anion exchange medium comprising fixed cationic groups and free anions X is placed in a hydrogen generator,

X ^" being an anion selected from the group consisting of S0 ₃ ^{2 ~} , S ₂ O ₅ ^2" , S ₂ O ₇ ^{2 "} , NO ₂ ^" , and mixtures thereof;

oxygen gas is trapped according to one of claims 1 to 6;

hydrogen is generated.

A process for trapping gaseous oxygen and purifying hydrogen in a hydrogen generator, comprising the steps of:

placing in an hydrogen generator an ion exchange support consisting of:

^■ at least one anion exchange medium comprising fixed cationic groups and free anions X ^", ^X" is an anion selected from the group consisting of S0 ₃ ^{2 ~,} S2O5 ^{2 ",} ^{2 S2O7"} ^~ N0 _2, and mixtures; and

^■ at least one cation exchange carrier comprising free cations

C _t ⁺ ;

oxygen gas is trapped according to one of claims 1 to 6;

hydrogen is generated;

the hydrogen is purified by contacting the generated hydrogen with the ion exchange support.

Process according to Claim 8, characterized in that the free cations C _t ⁺ are chosen from the group comprising the Na ⁺ , H ⁺ , K ⁺ ions and their mixtures.

Oxygen scavenging method according to one of Claims 1 to 9, characterized:

In that the anion exchange support has an exchange capacity of between 0.8 eq / L and 4.5 eq / L; and

In that the cationic fixed groups of the anion exchange support are groups chosen from the group comprising:

-NH ₃ ⁺ ; -NR ₃ ⁺ ; -NHR ₂ ⁺ ; -NH ₂ R ⁺ ; -N (ROH) (R ') ₂ ⁺ ; and -SR ₂ ⁺ ; R and R 'being alkyl or aryl. Apparatus for trapping gaseous oxygen, comprising an anion exchange support, said anion exchange support comprising fixed cationic groups and free X ^" anions,

X ^" being an anion selected from the group consisting of S0 ₃ ^{2 ~} , S2O5 ^2" , S2O7 ^{2 "} , N0 ₂ ^~ , and mixtures thereof.

Device for trapping gaseous oxygen according to claim 11, characterized in that the anion exchange medium has an exchange capacity of between 0.8 eq / L and 4.5 eq / L.

Device for trapping gaseous oxygen according to claim 10 or 11, characterized in that the fixed cationic groups are chosen from the group comprising: