Hydrogen production process and catalyst using plasma to catalyze ammonia decomposition

Abstract

The invention relates to a method for converting NH3-containing gases in the presence of a cold plasma, preferably a plasma generated by dielectric barrier discharge (DBD), and a catalyst comprising a support comprising alumina, nickel and at least one iron-containing accelerator. The invention also relates to said catalyst and to the use thereof for the production of high value added molecules such as hydrogen (H2).

Description

Technical Field

[0001] The present invention belongs to the field of chemical conversion, in particular to convert ammonia (NH 3 ) gas or gas mixture to produce hydrogen (H 2 ) and nitrogen (N 2 In particular, the present invention relates to the reaction of NH 3 Converted to H 2 and N 2 The invention relates to a method for producing a cold plasma, such as by dielectric barrier discharge (so-called DBD), which enables chemical conversions by plasma-catalysis. The invention also relates to said catalyst, a method for preparing said catalyst and the use of said catalyst for converting ammonia and producing high added value molecules, such as hydrogen. Background Art

[0002] With the substantial growth in energy demand and the impact of fossil fuels on the environment, finding new energy sources has attracted more and more attention.

[0003] Hydrogen fuel is considered to be an ideal choice for solving energy and environmental crises. In addition, its use in fuel cell vehicles is essential for controlling CO2 in the environment from traditional fossil fuels. x and NO x Emissions are particularly promising. Hydrogen has a higher energy density (142 MJ / kg) than other fuels. In addition, the molecule is easily obtained from water and gaseous hydrocarbon fuels. Many studies have examined hydrogen production methods such as steam reforming and water fractionation [1].

[0004] Ammonia (NH 3 ) is a promising candidate for transporting and storing hydrogen. In addition, 150 million tons of NH are produced and used each year worldwide. 3 Due to its storage properties, NH 3 It is more advantageous than other energy carriers of hydrogen: On the one hand, NH 3 The weight density of NH 3 The cost of the energy stored per volume is three times lower than that of hydrogen. In particular, ammonia decomposition is used in at least two different areas related to energy and environmental science: it can be used in particular to provide fuel cells with CO2-free x The hydrogen produced can also be used to remove ammonia from the reformate of internal gasification combined cycle (IGCC) power plants. This technology can be used as a CO 2 The removal method is widely used.

[0005] In recent years, NH 3 The decomposition of x H 2To date, conventional heterogeneous catalysis according to Equation 1 (Eq. 1) is the decomposition of NH 3 The main methods are [1], [2], [3].

[0006]

[0007] Given that NH 3 High chemical stability. Conventional thermal catalytic processes require high gas pressure and a large amount of energy (heat energy), especially temperatures of 500°C to 800°C, to promote catalyst activation, change thermodynamic equilibrium and ensure acceptable yields. High-temperature catalytic reactions not only lead to high energy consumption, but also the catalyst may be deactivated due to sintering of metal active sites and formation of coke on the catalyst surface. In general, thermal processes use precious metals (such as Ir, Pd, Pt, Rh and Ru) for catalysis and stable operation. The precious metal ruthenium (Ru) has the best catalytic activity for the decomposition of ammonia, but its cost and scarcity limit its large-scale commercialization. Unfortunately, nitrogen atoms (N ads ) is very slow in recombination and desorption, which inhibits the entire ammonia decomposition process unless the reaction is carried out at high temperature (about 500℃-800℃) [1], [2], [3].

[0008] Therefore, it is of great interest to find new processes that can operate at low temperatures and catalysts whose stability depends on temperature.

[0009] Different studies have been conducted to develop chemical synthesis techniques using cold plasmas, thus overcoming the above-mentioned temperature problems. Among these techniques, dielectric barrier discharge (DBD) has been described, in particular in combination with the presence of heterogeneous catalysts (plasma-catalysis) [4], [5].

[0010] In order to improve the conversion of ammonia, the prior art has tested different catalytic systems, plasma types, experimental variables and reactors. However, the efficiency of these systems remains low. In addition, the activity, stability and cost of the catalysts have proven to be unsuitable for industrial use [6], [7].

[0011] In particular, the object of the present invention is to provide a method for chemically converting ammonia (NH 3 ), wherein the catalyst has high catalytic activity and energy rate and is suitable for large-scale utilization, and the purpose is to obtain hydrogen (H 2 ) Also avoid using precious metals.

[0012] None of the documents [6], [7], [8], [9],

[10] ,

[11] or

[12] describe the plasma-catalytic conversion of ammonia (NH ) in the presence of a cold plasma and a catalyst comprising an alumina-based support, nickel and at least one iron (Fe)-containing promoter. 3) method. Summary of the invention

[0013] The first object of the present invention is to convert ammonia (NH 3 ) gas or gas mixture into hydrogen (H 2 ) and nitrogen (N 2 ) method: NH 3 →3 / 2H 2 +1 / 2N 2 The method is carried out in the presence of cold plasma and a catalyst comprising an alumina-containing support, nickel (Ni) and at least one promoter containing iron (Fe).

[0014] A second object of the invention is a catalyst, also called a catalytic system, which allows the reaction of ammonia (NH 3 ) gas or gas mixture into hydrogen (H 2 ) and nitrogen (N 2 ), the conversion is carried out in the presence of cold plasma, characterized in that the catalyst comprises a support containing aluminum oxide, nickel and at least one promoter containing iron (Fe). This catalytic system, which can be activated by DBD plasma, for example, can solve all the disadvantages of the prior art in thermal processes (high temperature and high pressure) and can produce NH under atmospheric conditions with high yields compared to the studies described in the prior art. 3 Synthetic H 2 .

[0015] According to a preferred embodiment, the catalyst comprises:

[0016] - a support comprising aluminum oxide,

[0017] -nickel,

[0018] - a promoter containing iron (Fe), and

[0019] -optionally at least one second accelerator:

[0020] - transition metal type promoters, in particular promoters containing cobalt (Co), manganese (Mn), copper (Cu) or silver (Ag);

[0021] - lanthanide-type promoters, in particular promoters containing lanthanum (La), cerium (Ce) or gadolinium (Gd);

[0022] - alkaline earth metal type accelerators, in particular accelerators containing barium (Ba); and / or

[0023] - Alkali metal type accelerators, especially accelerators containing potassium (K).

[0024] A third object of the present invention relates to a method for preparing said catalyst.

[0025] A fourth object of the present invention relates to the use of the catalyst of the present invention for converting 3 ), the conversion being carried out in the presence of a cold plasma, preferably a plasma generated by a dielectric barrier discharge (DBD).

[0026] The present invention allows to overcome all the drawbacks of the traditional thermocatalytic methods described in the prior art, obtaining a high catalytic and energetic efficiency, thus making it possible to exploit them on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Other features, objects and advantages of the present invention will become apparent from the following description which is intended to be illustrative only and not restrictive and which may be read with reference to the accompanying drawings:

[0028] [ Figure 1 ]GC spectrum of the inlet gas before the reaction when the catalytic system 5Ni10FeAl was combined with the DBD plasma catalytic reactor. Figure 1 The inlet gas of the DBD reactor (containing 100% NH 3 )’s GC spectrum.

[0029] [ Figure 2 ]GC spectrum of outlet ammonia after the catalytic system 5Ni10FeAl is combined with the DBD plasma catalytic reactor for reaction. Figure 2 The NH 3 GC spectrum of the remaining ammonia after conversion.

[0030] [Table 1] The table shows the catalytic activities (ie, conversion, selectivity) of several catalysts of the present invention and comparative catalysts tested in DBD plasma. DETAILED DESCRIPTION

[0031] definition

[0032] In the present invention:

[0033] - the expression "between ... and ..." (eg a numerical range) is to be understood as including the limit value (eg the limit value of the numerical range);

[0034] - any description relating to one embodiment is applicable to and interchangeable with all other embodiments of the invention;

[0035] - the expression "and / or" should be understood as "and" and "or"; for example, the expression "A and / or B" should be understood as A and B, or only A, or only B;

[0036] - the expression "N, M and / or P" is understood to mean "N and / or M and / or P";

[0037] - the expression "N, M and P" shall be understood to mean "N and M and P";

[0038] - Where an element or ingredient is included in and / or selected from a list of elements or ingredients, it should be understood that the individual elements or ingredients may be selected and combined with other individual elements, or may be selected to form a subgroup of two or more of the elements or ingredients explicitly listed; in addition, any element or ingredient mentioned in a list of elements or ingredients may be omitted from that list.

[0039] In the present invention, the term "DBD - dielectric barrier discharge" describes an electric discharge generated between two conductive elements separated by one or more dielectric elements.

[0040] In the present invention, the term "dielectric" describes an electrically insulating material that provides electrical insulation between the high voltage grid associated with the electrodes and the electrically conductive and thermally conductive pipes that are grounded through the reactor. This type of electrically insulating material is also used inside DBD cells to generate dielectric barrier discharge (DBD) plasma by promoting the accumulation of charge on the surface of this material.

[0041] In the present invention, the terms "catalyst" and "catalytic system" are used interchangeably and refer to a material that promotes a chemical reaction of an active species, such as a reagent fluid.

[0042] In the present invention, the term "plasma-catalysis" refers to a process in which a plasma discharge combined with a catalyst is performed.

[0043] The term "hydrogen" is understood to mean hydrogen gas (H 2 ).

[0044] In the present invention, the term "support" or "catalyst support" refers to a solid material or a mixture of solid materials, particularly characterized by the specific surface area on which the promoter is deposited.

[0045] In the present invention, the term "promoter" or "catalyst promoter" refers to a solid material or a mixture of solid materials that is usually added in small amounts to the surface of a support material to improve the efficiency and performance of the catalyst.

[0046] Of course, the present invention is described above by way of example. It should be appreciated that those skilled in the art can implement different variations of the present invention without departing from the scope of the present invention.

[0047] Conversion of NH 3 The gas method

[0048] The first object of the present invention relates to the reaction of ammonia (NH3 ) gas or gas mixture into hydrogen (H 2 ) and nitrogen (N 2 ) method: NH 3 →3 / 2H 2 +1 / 2N 2 , the method is carried out in the presence of cold plasma and a catalyst, the catalyst comprising:

[0049] - a support comprising aluminum oxide,

[0050] - Nickel, and

[0051] - At least one promoter containing iron (Fe).

[0052] The gases considered here include NH 3 , and possibly other chemicals. Therefore, this may include the conversion of NH 3 The purpose of this method is to produce high added value molecules, especially in gaseous form. In fact, the method of the invention allows the production of hydrogen (H 2 ), nitrogen (N 2 ) or a mixture thereof. The product of the process of the invention may also be in another form, such as a partially liquid or anhydrous form. In this case, it may consist of hydrazine, ammonium nitrate and / or ammonia.

[0053] Therefore, according to the present invention, the conversion of NH 3 The method is carried out in the presence of a catalyst and a cold plasma (preferably generated by dielectric barrier discharge (DBD)). During the implementation of the method of the present invention, the catalyst is activated by the cold plasma. The synergistic effect of plasma catalysis in the method has the effect of NH 3 Direct synthesis of high value-added gas H 2 The catalyst used in the present invention, which comprises a support containing aluminum oxide, nickel and at least one promoter containing iron (Fe), is combined with cold plasma and described in more detail below. Therefore, the method of the present invention is carried out in the presence of a catalyst activated by cold plasma. It should be noted that all the features described about the catalyst are applicable to the conversion method of the present invention.

[0054] According to one embodiment, the selected catalyst is placed between the electrodes of a DBD reactor, the gaseous material is circulated, and the catalyst is activated by a high voltage discharge (several kV) in a few nanoseconds to a few microseconds. This polarization, combined with adsorption, desorption and catalyst / gas interaction, leads to the formation of plasma and its activation and the production of hydrocarbons. During positive and negative polarization, the electrical energy supplied to the fixed bed in the form of sinusoidal or pulsed high voltage generates multiple currents on the HV (high voltage) carrier. These streamers, which range from a few hundred picoseconds to a few tenths of a nanosecond, are responsible for the negative or positive polarization of the catalytic sites.

[0055] Prior to the conversion, in particular the hydrogenation step, the catalytic system of the invention, in the case of its components in oxidic form, is advantageously heated in a cold plasma, preferably a DBD plasma, in the presence of H 2 As discharge gas for in-situ reduction.

[0056] The catalytic system of the present invention is activated by generating a strong electric field at the catalytic system (particularly between the particles of the catalytic system) or in its vicinity (in the gas flow, upstream or downstream of the catalytic system), the strong electric field being generally between 10 3 and 10 10 V / m and can vary with time. This strong electric field can ionize part of the gas and excite the atoms and molecules present in the gas phase. The walls of the reactor are typically made of metal materials; alternatively, in the case of using DBD plasma, the walls of the reactor are made of dielectric materials such as quartz, alumina or ceramics. Advantageously, the reactor can be cylindrical. In addition to producing a cold plasma state, the strong electric field generated is also responsible for the negative or positive polarization of the catalytic sites. This polarization causes adsorption and desorption reactions, including at low temperatures (for example, at temperatures below 400°C or below 350°C). The operating temperature of traditional non-polarized methods is higher, generally between 500°C and 800°C.

[0057] In particular, the reactor comprises at least one inlet and an outlet, the inlet being capable of supplying the gas to be converted, i.e. containing NH 3 The gas (or gas mixture) is discharged through the outlet, and the product is also in gaseous form.

[0058] In one variant of the invention, the catalytic system of the invention is activated by DBD plasma by providing an electrical power of less than 20-35 W / g of catalytic system (catalytic system present in the reactor, ie the catalytic bed).

[0059] Advantageously, the conversion reaction is carried out at a pressure close to or equal to atmospheric pressure (10 5 Pa) pressure, for example, 1.10 4 Pa to 3.10 5The DBD plasma is generated by applying a voltage between 1 and 25 kV, preferably between 2 and 20 kV, between two electrodes, in particular at a frequency between 1 kHz and 100 kHz. In particular, the gas hourly space velocity (GHSV) is 1000 h -1 and 150000h -1 Between, preferably less than 100000h -1 .

[0060] Optionally, there is a cooling system between the vessel for receiving the product produced by the conversion reaction and the outlet of the reactor in order to condense and remove liquid that may be formed during the conversion reaction.

[0061] Catalyst of the present invention

[0062] A second object of the present invention relates to a catalyst allowing the reaction of ammonia (NH 3 ) gas or gas mixture into hydrogen (H 2 ) and nitrogen (N 2 ), the conversion is carried out in the presence of cold plasma, characterized in that the catalyst comprises an alumina-based support, nickel and at least one promoter containing iron (Fe). This catalytic system, which can be activated by DBD plasma, for example, can solve all the disadvantages of the prior art in thermal processes (high temperature and high pressure) and can be used to convert NH into NH under atmospheric conditions with high yields compared to the prior art. 3 Synthetic H 2 .

[0063] Preferably, the catalyst of the present invention does not contain noble metals, such as ruthenium (Ru), iridium (Ir), palladium (Pd), platinum (Pt) or rhodium (Rh).

[0064] As shown in the following examples, the combined use of the catalyst of the present invention and a cold plasma, preferably a plasma generated by a dielectric barrier discharge (DBD), allows the production of high value-added molecules, such as hydrogen (H 2 ), and at the same time improve the catalytic performance of the reaction, namely NH 3 The conversion rate and the desired product (H 2 )’s selectivity.

[0065] Accordingly, the present invention generally relates to a catalyst comprising:

[0066] - a support comprising aluminum oxide,

[0067] - Nickel, and

[0068] - At least one promoter containing iron (Fe).

[0069] According to one embodiment, the present invention is directed to cold plasma activated catalysts.

[0070] In the present invention, the terms "catalytic system" and "catalyst" are interchangeable. According to one embodiment of the present invention, the catalytic system is a so-called mono / bimetallic catalytic system. It should be noted that the concepts of monometallic system and bimetallic system specifically relate to the substances present in the catalyst, without considering the support and nickel used. For example, in the case where the catalyst is doped with two promoters, it is called a "bimetallic catalyst"; in the case where the catalyst is doped with three promoters, it is called a "trimetallic catalyst".

[0071] The support used in the present invention is based on alumina. In particular, it is chosen for its ability to adsorb reagents (more particularly NH 3 ), its thermal stability and specific surface area. It is also chosen for its dielectric properties, which affect the properties of the plasma due to the dielectric constant and the polarization effect that produces the local electric field, changing the DBD discharge behavior, electric field and electron density of the plasma. The inventors have recognized that the use of a support containing aluminum oxide is particularly advantageous, especially compared to the supports described in the literature (such as SiO 2 ) in order to obtain a higher NH 3 The catalytic result of the transformation.

[0072] The support affects the physicochemical properties (basicity, acidity, reducibility, oxygen mobility due to inherent defects in the surface, etc.) as well as textural properties (pore volume, pore size, specific surface area, etc.) and electrical properties (dielectric constant, conductivity, etc.), which in turn regulate the catalytic performance of the system.

[0073] According to the invention, the support of the catalytic system comprises aluminum oxide; in particular, the support may consist of aluminum oxide. According to one embodiment, the support is aluminum oxide, such as Al 2 O 3 Therefore, the support of the catalytic system may also comprise further components, such as mixed oxides and / or cerium.

[0074] In the present invention, the alumina may have any specific surface area (measured in BET surface area m 2 For example, the specific surface area of ​​aluminum oxide is at least 20 m 2 / g, especially at 50 and 1000m 2 / g. For example, the specific surface area of ​​alumina is 200m 2 / g or 260m 2 According to one embodiment of the present invention, the catalyst comprises a carrier, the carrier comprises a catalyst having a specific surface area between 50 and 1000 m2 / g, between 100 and 800m 2 / g, between 150 and 300m 2 / g or between 180 and 250m 2 / g of aluminum oxide.

[0075] The preparation of the support of the catalytic system is described in detail below. The support used in the present invention may also be a commercially available support.

[0076] The catalyst of the invention also comprises nickel. The nickel in the catalyst of the invention may be in any of its oxidation states, in particular in metallic form (oxidation state 0) or in the form of an oxide in oxidation state II (e.g. in the form of nickel (II) oxide (NiO)). Advantageously, the mass content of nickel in the catalytic system may be between 0.1% and 50% by weight, for example between 0.5% and 40% or between 1% and 30%, relative to the weight of the support; preferably less than 20% or less than 15%. "The weight of the support" is to be understood as the "weight of the support containing alumina", including the weight when the support comprises elements other than alumina. In a particularly advantageous manner, the catalytic system comprises 5% by weight ± 1% by weight of nickel relative to the weight of the support.

[0077] By convention, a catalyst comprising 5 wt% nickel and 10 wt% iron relative to the weight of the alumina-containing support is denoted as "5Ni10FeAl", "5Ni10-Fe-Al" or "5Ni10Fe / Al".

[0078] The catalyst of the present invention comprises at least one promoter, i.e. one or more promoters. The at least one promoter acts as a dopant and affects the physicochemical, textural and conductive properties of the catalyst. Advantageously, the promoter of the present invention has suitable surface physicochemical properties to help fix the reagent NH 3 , as well as suitable dielectric properties, which allows improving the conductivity of the resulting catalyst and logically leads to the 3 Produces NH 2 , NH radicals, which are then desorbed from the catalytic surface, thereby promoting the formation of hydrogen.

[0079] The catalyst of the present invention comprises at least one promoter containing iron (Fe). The iron may be in any oxidation state, in particular in metallic form or in oxide form. For example, the iron promoter is in the form of FeO: iron (II) oxide or ferrous oxide, iron (III) oxide Fe 2 O 3 Or ferric oxide, or with NiO and Al 2 O 3An example of a catalyst representative of this embodiment is catalyst 5Ni10Fe-Al, ie a catalyst comprising an alumina-containing support, nickel and an iron-containing promoter.

[0080] The catalyst of the present invention may also comprise at least one second promoter. In particular, the second promoter may comprise a chemical element selected from the group consisting of transition metals, alkali metals, alkaline earth metals, lanthanides and mixtures thereof. In the present invention, the promoter is in any oxidation state thereof, in particular in metallic form or in oxide form. Therefore, according to one embodiment of the present invention, the catalyst comprises at least two promoters, i.e. two or more promoters, for example three or four promoters.

[0081] In the present invention, the transition metal may be selected in particular from the group consisting of copper, cobalt, silver, molybdenum, vanadium, manganese, chromium, yttrium, titanium and tantalum. In the case where the second promoter comprises a transition metal chemical element, the latter is preferably cobalt (Co), copper (Cu), silver (Ag) and / or manganese (Mn).

[0082] In the present invention, the alkali metal may be selected in particular from the group consisting of lithium, sodium, potassium, rubidium, cesium and francium. In the case where the second promoter comprises an alkali metal chemical element, the latter is preferably potassium (K) or cesium (Cs), even more preferably potassium (K).

[0083] In the present invention, the alkaline earth metal may in particular be selected from the group consisting of barium, calcium and magnesium. In the case where the second promoter comprises an alkaline earth metal chemical element, the latter is preferably barium (Ba).

[0084] In the present invention, the lanthanide element may be selected in particular from the group consisting of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium. In the case where the second promoter comprises a lanthanide chemical element, the latter is preferably cerium (Ce), gadolinium (Gd) and / or lanthanum (La), even more preferably cerium (Ce).

[0085] According to one embodiment of the present invention, the catalyst comprises at least one second promoter comprising cobalt (Co), manganese (Mn), copper (Cu) and / or silver (Ag).

[0086] According to one embodiment of the present invention, the catalyst comprises at least one second promoter comprising lanthanum (La), cerium (Ce) and / or gadolinium (Gd).

[0087] According to one embodiment of the present invention, the catalyst comprises at least one second promoter comprising barium (Ba).

[0088] According to one embodiment of the present invention, the catalyst comprises at least one second promoter comprising potassium (K).

[0089] According to a preferred embodiment, the catalyst of the present invention comprises at least one second promoter comprising cobalt (Co). An example of a catalyst representing this embodiment is catalyst 5Ni10Fe1Co-Al, i.e. a catalyst comprising two different promoters: a promoter comprising Fe and a promoter comprising Co.

[0090] The nickel and / or promoter content can be adjusted according to the nature of the promoter used and / or the type of conversion reaction performed.

[0091] According to one embodiment of the present invention, the mass content of the promoter in the catalytic system is between 0.1 wt % and 40 wt %, for example between 0.2 wt % and 30 wt %, in particular between 0.3 wt % and 20 wt %, preferably between 0.5 wt % and 15 wt %, in particular between 1 wt % and 12 wt %, even more preferably between 2 wt % and 10 wt %, relative to the weight of the carrier.

[0092] The promoters used to prepare the catalysts of the invention are in any oxidation state, in particular in metallic or oxide form. They may therefore contain other chemical elements which have not been taken into account in the calculation of the mass content stated. For example, for the catalyst 5Ni10Fe1Co-Al, if 1 g of a nickel-containing support is used, 0.049 g of the promoter Co(NO 3 ) 2 6H 2 O (molar mass: 291.04 g / mol), which corresponds to 0.01 g Co (molar mass: 58.93 g / mol), or 1 wt% cobalt relative to the weight of the support. For this catalyst, the mass content of promoter is 11 wt% relative to the weight of the support, i.e. 10% iron (or "iron promoter") and 1% cobalt (or "cobalt promoter").

[0093] According to one embodiment of the present invention, the mass content of Fe in the catalytic system is between 0.1 wt% and 40 wt%, for example between 0.2 wt% and 30 wt%, in particular between 0.3 wt% and 25 wt%, preferably between 0.5 wt% and 20 wt%, in particular between 1 wt% and 15 wt%, even more preferably between 2 wt% and 10 wt%, relative to the weight of the carrier.

[0094] According to one embodiment of the present invention, the mass content of other promoters (e.g., second promoters) in the catalytic system is between 0.1 wt% and 40 wt%, such as between 0.2 wt% and 30 wt%, in particular between 0.3 wt% and 20 wt%, preferably between 0.5 wt% and 15 wt%, in particular between 1 wt% and 12 wt%, even more preferably between 2 wt% and 10 wt%, relative to the weight of the carrier. For example, in addition to the Fe-containing promoter, the catalyst of the present invention further comprises 0.5 wt% to 20 wt% (wt% relative to the weight of the carrier) of one or more other promoters selected from the group consisting of cobalt (Co), manganese (Mn), copper (Cu), silver (Ag), lanthanum (La), cerium (Ce), gadolinium (Gd), barium (Ba) and potassium (K). According to another example, in addition to the Fe-containing promoter, the catalyst of the present invention further comprises 0.1 wt% to 4 wt% (wt% relative to the weight of the carrier) of cobalt (Co).

[0095] According to a particular embodiment of the present invention, the catalyst is doped with two promoters, one of which contains iron (Fe) and the other contains cobalt (Co). This catalyst is called a bimetallic catalyst. According to this embodiment, the mass content of iron in the catalyst can be preferably between 6% and 14%, between 7% and 13%, or between 6% and 12%. For example, the mass content of iron in the catalyst is 10% by weight ± 0.5% by weight relative to the weight of the carrier. In addition, according to this specific embodiment, the mass content of cobalt in the catalyst can be preferably between 0.1% and 4%, between 0.2% and 3%, or between 0.5% and 2%. For example, the mass content of cobalt in the catalyst is 1% by weight ± 0.5% by weight relative to the weight of the carrier. An example of a catalyst representing this embodiment is catalyst 5Ni10Fe1Co-Al, that is, the catalyst comprises a carrier containing aluminum oxide, 5% by weight of nickel relative to the weight of aluminum oxide, and two different promoters: 10% by weight of iron and 1% by weight of cobalt.

[0096] The catalyst may be in different forms, such as beads, monoliths, powders or granules. In powder form, the average size of the particles forming the powder may be between 1 μm and 1 mm, such as between 100 μm and 1 mm, in particular between 200 μm and 800 μm, preferably about 600 μm ± 20 μm. In particular, the size of the particles may be adjusted according to the production scale adopted. The catalyst may also have a geometric shape, advantageously beads with an average size of less than 5 cm. The average size of the catalyst is adjusted according to the type and size of the fixed bed reactor used to avoid any pressure drop.

[0097] According to one embodiment of the present invention, the support, nickel and at least one promoter form a homogeneous mixture. In particular, the nickel-modified support and promoter form a homogeneous mixture. This means that the nickel and promoter are evenly distributed throughout the volume of the catalyst.

[0098] According to a preferred embodiment, the catalyst of the present invention comprises:

[0099] - a support comprising aluminum oxide,

[0100] -nickel,

[0101] - a promoter containing iron (Fe), and

[0102] -optionally at least one second accelerator:

[0103] - transition metal type promoters, in particular promoters containing cobalt (Co), manganese (Mn), copper (Cu) or silver (Ag);

[0104] - lanthanide-type promoters, in particular promoters containing lanthanum (La), cerium (Ce) or gadolinium (Gd);

[0105] - alkaline earth metal type accelerators, in particular accelerators containing barium (Ba); and / or

[0106] - Alkali metal type accelerators, especially accelerators containing potassium (K).

[0107] According to another preferred embodiment, the catalyst of the present invention comprises:

[0108] - a support comprising aluminum oxide,

[0109] - 0.1 to 50% by weight of nickel (wt% relative to the weight of the support),

[0110] - 0.1 wt.% to 40 wt.% of a promoter (wt.% relative to the weight of the support), including at least one promoter containing iron (Fe), and optionally at least one second promoter:

[0111] - transition metal type promoters, in particular promoters containing cobalt (Co), manganese (Mn), copper (Cu) or silver (Ag);

[0112] - lanthanide-type promoters, in particular promoters containing lanthanum (La), cerium (Ce) or gadolinium (Gd);

[0113] - alkaline earth metal type accelerators, in particular accelerators containing barium (Ba); and / or

[0114] - Alkali metal type accelerators, especially accelerators containing potassium (K).

[0115] According to another preferred embodiment, the catalyst of the present invention comprises:

[0116] - a support comprising aluminum oxide,

[0117] - 0.1 to 50% by weight of nickel (weight % relative to the weight of the support), and

[0118] - 0.1 wt % to 40 wt % of a promoter (wt % relative to the weight of the support), including a promoter containing iron (Fe) and at least one second promoter, the second promoter being selected from promoters containing cobalt (Co), manganese (Mn), copper (Cu), silver (Ag), lanthanum (La), cerium (Ce), gadolinium (Gd), barium (Ba) and potassium (K).

[0119] According to another preferred embodiment, the catalyst of the present invention comprises:

[0120] - a support comprising aluminum oxide,

[0121] - 0.1 to 50% by weight of nickel (wt% relative to the weight of the support),

[0122] - 0.5 to 20 wt% of an iron (Fe) promoter (wt% relative to the weight of the support), and

[0123] - 0.5 to 20 wt. % of one or more promoters (wt. % relative to the weight of the support) chosen from cobalt (Co), manganese (Mn), copper (Cu), silver (Ag), lanthanum (La), cerium (Ce), gadolinium (Gd), barium (Ba) and potassium (K).

[0124] According to another preferred embodiment, the catalyst of the present invention comprises:

[0125] - a support comprising aluminum oxide,

[0126] - 0.1 to 50% by weight of nickel (wt% relative to the weight of the support),

[0127] - 0.5 to 20 wt% of an iron (Fe) promoter (wt% relative to the weight of the support), and

[0128] - 0.1 to 4 wt% cobalt (Co) promoter (wt% relative to the weight of the support).

[0129] Catalytic system preparation method

[0130] The preparation of the catalyst system of the present invention can be carried out according to different methods.

[0131] In particular, the catalytic system can be prepared by a method comprising contacting an alumina-containing support with a nickel precursor and at least one promoter (or promoters) precursor. This step allows the formation of a solid comprising the support, nickel and promoter (or promoters). Optionally, the method comprises a step of calcining the resulting mixture. The contacting step may be preceded by a step of modifying the support. In addition, the optional calcining step may be followed by a step of reducing the calcined mixture.

[0132] The step of contacting the support with the nickel precursor and the promoter precursor can be carried out, for example, by impregnation, coprecipitation or sol-gel. These three specific embodiments (also called sub-variants) will be described in more detail below.

[0133] The precursor of the nickel precursor and the promoter can be composed of any compound or mixture of compounds containing the metal used as the active metal / promoter, more specifically, it can be a salt of the metal, an oxide of the metal or a mixture thereof, preferably a salt of the metal or a mixture of salts of the metal. For example, the salt of the metal (referring to a non-hydrated salt or a hydrated salt, or a multi-hydrated salt) can be selected from chlorides, nitrates, sulfates, carbonates, acetates, acetylacetonates, tartrates and citrates of the metal and mixtures thereof, preferably nitrates of the metal. In the case where the promoter is a mixture of several metals, the precursor can be a mixture of different types of salts and / or oxides of these metals.

[0134] The calcination step results in oxidation of the different components of the catalytic system (support, nickel and promoter). In turn, the optional calcination step may be optionally followed by a reduction step, thereby changing the oxidation state of the nickel and promoter (with nickel and metallic promoter) and possibly the oxidation state of the support. The reduction may be a full or partial reduction, i.e. only part of the components of the catalytic system may be reduced. The reduction step may be carried out in situ in a non-thermal plasma device under hydrogen.

[0135] According to a first variant of the method of the present invention, the method for preparing the catalytic system of the present invention comprises:

[0136] - a step of contacting the alumina-containing support with a nickel precursor and with a precursor of one or more promoters, and

[0137] - Optionally, a step of calcining the mixture obtained after contacting the components,

[0138] - Optionally, a step of reducing the calcined mixture obtained in the previous step.

[0139] According to a second variant of the method of the present invention, the method for preparing the catalytic system of the present invention comprises:

[0140] - a step of contacting the alumina-containing support with a nickel precursor and with a precursor of one or more promoters, and

[0141] - a step of calcining the mixture obtained after the contacting of the components,

[0142] - Optionally, a step of reducing the calcined mixture obtained in the previous step.

[0143] According to a third variant of the method of the present invention, the method for preparing the catalytic system of the present invention comprises:

[0144] - a step of contacting the alumina-containing support with a nickel precursor and with a precursor of one or more promoters, and

[0145] - a step of calcining the mixture obtained after the contacting of the components,

[0146] - A step of reducing the calcined mixture obtained in the previous step.

[0147] According to a fourth variant of the method of the present invention, the method for preparing the catalytic system of the present invention comprises:

[0148] - a step of modifying the support comprising alumina, and

[0149] - a step of contacting the modified support with a nickel precursor and with a precursor of one or more promoters,

[0150] - Optionally, a step of calcining the mixture obtained after contacting the components,

[0151] - Optionally, a step of reducing the calcined mixture obtained in the previous step.

[0152] In particular, the step of contacting the components can be performed by impregnation. More specifically, according to a first sub-variant, the method comprises the following steps:

[0153] 1) a step of preparing a carrier, and

[0154] 2) A step of contacting the components by impregnation.

[0155] Furthermore, step 1) of preparing the carrier comprises the following sub-steps:

[0156] 1.1) Preparing a suspension containing an aluminum oxide precursor or an aluminum oxide precursor.

[0157] According to this step 1.1), the support precursor corresponds to an aluminum oxide precursor or a mixture of several precursors. In the case where the support is a mixture of cerium and aluminum oxide, in particular a mixed oxide, it is advantageous to prepare a cerium precursor suspension and an aluminum oxide precursor suspension separately and then mix them in a certain ratio to obtain the desired Ce / Al molar ratio in the final mixture, in particular a mixed oxide of cerium and aluminum oxide.

[0158] 1.2) Mix the suspension obtained in step 1.1).

[0159] In particular, the addition of these precursors is carried out at room temperature, for example at a temperature of 20 to 25° C., with continuous mixing for 30 minutes to several hours, for example 30 minutes to 3 hours.

[0160] 1.3) Recovering the solid obtained in step 1.2) by removing excess water, in particular by evaporating the water or filtering, and then drying the solid obtained.

[0161] In particular, the drying step may be carried out at a temperature below 150°C, typically at a temperature of about 100°C, for example for 5 to 48 hours.

[0162] 1.4) Calcining the solid obtained in step 1.3) to obtain a carrier.

[0163] The product obtained in step 1.3) is calcined, for example at a temperature between 300° C. and 600° C. The calcination step may be carried out for 3 hours or more, for example 3 hours to 6 hours. This step results in thermal decomposition of the nitrate to obtain the oxide.

[0164] Furthermore, the step 2) of contacting the components comprises the following sub-steps:

[0165] 2.1) An aqueous suspension of precursors comprising a nickel precursor and one or more promoters is prepared.

[0166] During this step, an appropriate mass of each precursor is added to an appropriate volume of solvent, such as water. "Appropriate mass" and "appropriate volume" should be understood as the appropriate amount of precursor and solvent (especially water) required to obtain the desired mass content of nickel and promoter in the final catalytic system.

[0167] 2.2) adding the carrier obtained in step 1) to the aqueous solution obtained in step 2.1) to obtain a suspension,

[0168] 2.3) Mix the suspension obtained in step 2.2).

[0169] The addition of these precursors is continued with mixing at room temperature, for example at a temperature between 20 and 25° C., for 30 minutes to several hours, for example 30 minutes to 3 hours.

[0170] 2.4) recovering the solid comprising the support, nickel and the promoter obtained in step 2.3) by removing excess water, in particular by evaporating the water or filtering, and then drying the obtained solid.

[0171] For example, the drying step may be carried out at a temperature below 150°C, typically at a temperature of about 100°C, for 7 to 48 hours.

[0172] 2.5) Calcining the solid obtained in step 2.4) to obtain a catalytic system.

[0173] The product obtained in step 2.4) is calcined, for example at a temperature between 300° C. and 600° C. The calcination step may be carried out for 3 hours or more, for example 3 hours to 6 hours. This step results in thermal decomposition of the nitrate to obtain the oxide.

[0174] This first alternative is also called the wet impregnation process. It consists in impregnating the support with a nickel precursor and a precursor of a promoter.

[0175] Alternatively, the step of contacting the components can be performed by coprecipitation. More specifically, according to a second sub-variant, the method for preparing the catalytic system comprises:

[0176] 1') a step of preparing a vector, and

[0177] 2') A step of contacting the support with a nickel precursor and a promoter, the contacting being carried out by coprecipitation.

[0178] Step 1') of preparing the support consists of preparing an aqueous solution containing a nickel precursor and a precursor of a promoter. This step is identical to step 2.1) of the aforementioned wet impregnation process.

[0179] Furthermore, the step 2') of contacting the components comprises the following sub-steps:

[0180] 2.1') ​​Add the carrier to the solution obtained in step 1') to obtain a suspension.

[0181] This step is the same as step 2.2) of the aforementioned wet impregnation process.

[0182] 2.2') To the suspension obtained in step 2.1') ​​a base is added.

[0183] In this step, a base is added to the suspension obtained in step 2.1'). Advantageously, this base is a hydroxide salt, such as sodium hydroxide, potassium hydroxide, sodium carbonate or potassium carbonate, preferably sodium hydroxide. It can be used in the form of a solution, in particular an aqueous solution. The base is gradually added dropwise until the pH value of the suspension (consisting of a solid suspension in a liquid solution) is between 8 and 12, preferably approximately equal to 10. Step 2.2') is carried out at a temperature between 60°C and 100°C, in particular between 70°C and 90°C, preferably approximately equal to 80°C.

[0184] 2.3') Mix the suspension obtained in step 2.2').

[0185] The purpose of this step is to precipitate nickel hydroxide and the hydroxide of the metal used as promoter on the surface of the support. For example, mixing, in particular mixing by stirring, is carried out at a temperature between 60° C. and 100° C., preferably about equal to 80° C. This mixing step can be carried out for 2 hours or more, generally about 3 hours.

[0186] 2.4') Recovering the solid containing the support, nickel and promoter obtained in step 2.3') and calcining it to obtain a catalytic system.

[0187] This step is the same as step 2.5) of the wet impregnation process.

[0188] This second sub-variant allows the precipitation of nickel hydroxide and of the hydroxide of the metal used as promoter on the surface of the support.

[0189] The step of contacting the components can also be performed by a sol-gel reaction. More specifically, according to a third sub-variant, the step of contacting the support with the precursor of the nickel precursor and the promoter is performed by a sol-gel reaction and comprises the following sub-steps:

[0190] 1") preparing a citric acid solution comprising a nickel precursor, a precursor of one (or more) promoters and a carrier precursor, 2") adjusting the pH of the solution 1") to, for example, 4, preferably by adding a strong alkaline solution of NaOH,

[0191] 3") heating the solution of step 2") under reflux, and

[0192] 4”) remove excess citric acid and recover the catalyst system.

[0193] In step 1″), the support precursor corresponds to an aluminum oxide precursor, a cerium precursor, a lanthanum precursor or a mixture of an aluminum oxide precursor with cerium and lanthanum precursors, depending on whether the support is aluminum oxide, cerium, lanthanum or a mixture of aluminum oxide, cerium and lanthanum. In the case where the support is a mixture of aluminum oxide, cerium and lanthanum, in particular a mixed oxide, it is advantageous to prepare a solution of an aluminum oxide precursor and a solution of a cerium and lanthanum precursor separately and then mix them in such proportions as to obtain the desired Al / Ce and Ce / La molar ratios in the final mixture of cerium and lanthanum aluminum oxide, in particular a mixed oxide.

[0194] To prepare the desired content of catalyst, the precursor of the support as well as the nickel precursor (e.g. nickel (II) acetate tetrahydrate) and the promoter are advantageously dissolved separately in citric acid and particularly heated (e.g. at 80-120° C., particularly at about 80° C., for 1 hour or more, e.g. about 2 hours).

[0195] The reflux heating step (3") is carried out for a sufficient time to obtain a gel.

[0196] If the product obtained in step 3") is a gel, it can be dried or solidified in an oven, in particular using liquid nitrogen, before a possible calcination step, so that the product of step 3") is solid.

[0197] The last step 4") consists of recovering the solid obtained in step 3") and is identical to step 2.5) of the wet impregnation process.

[0198] The carrier used in the preparation of the catalyst system can also be a commercially available carrier.

[0199] Use of the catalyst of the present invention

[0200] The present invention also relates to the use of the catalyst of the present invention for converting ammonia (NH 3 ) and the conversion is carried out in the presence of a cold plasma.

[0201] The present invention particularly relates to the catalyst of the present invention and to cold plasma, preferably plasma generated by dielectric barrier discharge (DBD), for converting NH 3 Combination of gases or gas mixtures.

[0202] In other words, the present invention relates in particular to the catalyst according to the present invention activated by cold plasma, preferably plasma generated by dielectric barrier discharge (DBD), for the conversion of NH 3 The use of gases or gas mixtures.

[0203] In fact, the inventors have recognized that the combination of the catalyst of the present invention and a cold plasma, preferably a plasma generated by a dielectric barrier discharge (DBD), leads to the conversion of NH 3 gas or gas mixture and / or produce hydrogen, for example produce hydrogen (H 2 ) and gaseous nitrogen (N 2 )’s efficiency is improved.

[0204] The present invention also relates to the use of the catalytic system according to the invention in the production of NH 3 Gas or gas mixture to produce hydrogen (H 2 ) and nitrogen (N 2 )’s purpose.

[0205] The present invention particularly relates to the catalyst of the present invention and to the use of cold plasma, preferably plasma generated by dielectric barrier discharge (DBD), for the production of NH 3 Gas or gas mixture to produce hydrogen (H 2 ) and nitrogen (N 2 ) combined use.

[0206] The present invention particularly relates to the use of the catalyst according to the invention activated by cold plasma, preferably plasma generated by dielectric barrier discharge (DBD), for the production of NH 3 Gas or gas mixture to produce hydrogen (H 2 ) and nitrogen (N 2 )’s purpose.

[0207] Citation list

[0208] [1]Yoshitsugu Kojima,Masakuni Yamaguchi,Ammonia as a hydrogen energy carrier,International Journal of Hydrogen Energy,2022,ISSN 0360-3199,https: / / doi.org / 10.1016 / j.ijhydene.2022.05.096.

[0209] [2]Schüth,F.and Palkovits,R.and R.and Su,DS,Ammonia as a possible element in an energy infrastructure:catalysts for ammoniadecomposition,Energy Environ.Sci.,2012,Volume 5,p.6278-6289,http: / / dx.doi.org / 10.1039 / C2E E02865D.

[0210] [3]Dejiang Zhou, Renwu Zhou, Rusen Zhou, Baowang Liu, Tianqi Zhang, Yubin Xian, Patrick J.

[0211] Cullen,Xinpei Lu,Kostya(Ken)Ostrikov(2021).Sustainable ammonia production by non-thermal plasmas:Status,mechanisms,andopportunities.Chemical Engineering Journal,(),-.

[0212] http: / / doi.org / doi:10.1016 / j.cej.2021.129544

[0213] [4]M.Mikhail et al.,《Tailoring physicochemical and electricalproperties of Ni / CeZrOx doped catalysts for high efficiency of plasmacatalytic CO2 methanation》,Appl.Catal.B Environ.,vol.294,p.120233,oct.2021,https: / / doi.org / 10.1016 / j.apcatb.2021.120233

[0214] [5]M.Mikhail et al.,《Electrocatalytic behaviour of CeZrOx-supportedNi catalysts in plasma assisted CO2 methanation》,Catal Sci Technol,vol.10,no114,p.4532-4543,2020,https: / / doi.org / 10.1039 / D0CY00312C

[0215] [6]Mao Akiyama,Keigo Aihara,Tomiko Sawaguchi,Masahiko Matsukata,Masakazu Iwamoto,Ammonia decomposition to clean hydrogen using non-thermalatmospheric-pressure plasma,International Journal of Hydrogen Energy,Volume43,Issue 31,2018,Pages 14493-14497,ISSN 0360-3199,https: / / doi.org / 10.1016 / j.ijhydene.2018.06.022.

[0216] [7] MostafaEl-Shafie, Shinji Kambara, Yukio Hayakawa, Plasma-enhancedcatalytic ammonia decomposition over ruthenium(Ru / Al2O3) and sodaglass(SiO2)materials, Journal of the Energy Institute, Volume 99, 2021, Pages 145-153, ISSN1743-9671, https: / / doi.org / 10.1016 / j.joei.2021.09.001.

[0217] [8]Lucentini et al., "Review of the decomposition of ammonia togenerate hydrogen" Ind.Eng.Chem.

[0218] Res.2021,60,18560-18611,https: / / doi.org / 10.1021 / acs.iecr.1c00843

[0219] [9]Demand de brevet CN 101147863 A

[0220]

[10] Demande de brevet EP 2 332 646 A1

[0221]

[11] Demand de brevet WO 2021 / 255422 A1

[0222]

[12] Yanhhui Yi et al., Plasma-assisted ammonia decomposition over Fe-Ni alloy catalysts for COx-free hydrogen" AlChE J, 65:691-701, 2019, https: / / doi.org / 10.1002 / aic.16479

[0223] Example

[0224] The present invention will now be described in more detail with reference to the following examples, which are intended to be illustrative rather than limiting the scope of the present invention.

[0225] A. Preparation of different catalytic systems by wet impregnation

[0226] Various catalytic systems, more specifically identified in Table 1 below, were prepared using several supports:

[0227] 1) Commercially available alumina (A1200, specific surface area = 200m 2 / g, Saint Gobain);

[0228] 2) Commercially available alumina (Al260, specific surface area = 260 m 2 / g, Saint Gobain);

[0229] 3) Commercially available ceria-zirconia mixed oxide (CZ) from Sigma-Aldrich;

[0230] 4) Commercially available silicon dioxide (Si160, specific surface area = 160 m 2 / g, Saint Gobain);

[0231] 5) Commercially available magnesium oxide MgO from Sigma-Aldrich;

[0232] 6) The mixed oxide synthesized by the inventor according to the aforementioned process.

[0233] The various catalysts given here as examples were prepared by wet impregnation.

[0234] By this method, Ni(NO 3 ) 2 6H 2 The nickel catalytic system doped with a promoter (metal M) was prepared by an aqueous solution of Fe(NO 3 ) 2 9H 2 O,Co(NO 3 ) 2 6H 2 O、Mn(NO 3 ) 2 ·4H 2 O、La(NO 3 ) 2 6H 2 O、Y(NO 3 ) 2 6H 2 O.Gd(NO 3 ) 3 6H 2 O、Ba(NO 3 ) 2 Ag(NO 3 )、Cs(NO 3 )、Ce(NO3 ) 3 6H 2 O, Cu(NO 3 ) 2 ·5H 2 O.NaNO 3 and KNO 3 (both commercially available, Sigma-Aldrich), depending on the desired accelerator.

[0235] For example, to prepare catalyst 5Ni10Fe-Al (one of the catalysts of the present invention), the nickel content is 5 wt % relative to the weight of the carrier, and the content of the Fe promoter is 10 wt % relative to the weight of the carrier.

[0236] At room temperature and under stirring, the nickel salt and promoter precursor of appropriate mass are dissolved in 50mL volume of water. The carrier of appropriate mass is added to the aqueous solution containing the metal salt mixture and stirred for 2 hours. For example, 0.25g nickel nitrate (which represents 5% by weight of nickel content relative to the weight of the carrier), 0.72g ferric nitrate (which represents 10% by weight of iron content relative to the weight of the carrier) and 1g of the carrier are mixed according to the aforementioned steps. The mixture is then placed in a rotary evaporator at 60°C to remove excess water.

[0237] After impregnation and evaporation of water, all samples were collected, dried in an oven at 100°C for 8 hours, and then calcined in air at 550°C at a rate of 10°C / min for 4 hours. After calcination, samples of the catalytic system were manually ground and sieved to an average particle size between 50 and 200 μm.

[0238] The various catalysts prepared according to the above method are listed in Table 1 below.

[0239] B. NH 3 of Gas conversion

[0240] The steps of producing hydrogen by a catalytic plasma reactor are as follows: 320 mg of the catalyst to be tested (corresponding to GHSV (gas hourly space velocity) 22000 h -1 ) was placed between the electrodes of the DBD reactor; ammonia gas was supplied to the reactor at a total flow rate of 160 mL / min STP (standard temperature and pressure) at atmospheric pressure and a temperature of 20°C.

[0241] A non-thermal dielectric barrier discharge (DBD) plasma was generated between two electrodes: a cylindrical electrode made of copper placed inside a tube made of alumina (3 mm in diameter), surrounded by a coaxial tube made of quartz (10 mm in inner diameter, 1 mm in thickness), and a steel wire wound on the outer surface of the tube made of quartz was used as a ground electrode (grounded via an external capacitor of 2 nF). In this configuration, the discharge was sustained within a space of 2.5 mm, covering a length of about 1 cm. Prior to the catalytic test, the synthesized catalytic system was heated in H 2 In-situ reduction was performed for 60 min under non-thermal DBD plasma as the discharge gas.

[0242] The activity and selectivity of the catalysts with and without promoters under DBD plasma conditions were evaluated in an experimental setup consisting of a tubular cylindrical reactor made of quartz, a DBD plasma generator and corresponding devices for gas supply and analysis.

[0243] Without plasma, no change in the outlet gas composition was observed. When the plasma was ignited, hydrogen and nitrogen were obtained at the outlet after stabilization.

[0244] The following equations were used to estimate the catalytic performance and calculate the NH 3 The conversion rate and H 2 and N 2 Selectivity:

[0245]

[0246]

[0247]

[0248] where F in and F out Refers to the inlet and outlet flow rates of the substance under consideration at the reactor inlet and outlet respectively (mol / s).

[0249] C. Results

[0250] Table 1 below illustrates and summarizes the list of catalysts tested and shows the 3 Conversion rate and H 2 and N 2 The catalytic activity results obtained in terms of selectivity.

[0251] [Table 1]

[0252]

[0253]

[0254] Figure 1The 5Ni10FeAl catalytic system (catalyst 12i in Table 1 above) is combined with a DBD plasma catalytic reactor to perform the reaction with a pre-gas (containing 100% NH 3 )’s GC spectrum.

[0255] Figure 2 The 5Ni10FeAl catalytic system (catalyst 12i in Table 1 above) is combined with a DBD plasma catalytic reactor to react NH 3 GC spectrum of residual ammonia after conversion.

Claims

1. A method for converting a gas or gas mixture containing ammonia (NH3) into hydrogen (H2) and nitrogen (N2) according to the following reaction: It is characterized in that It is carried out in the presence of cold plasma and a catalyst comprising: - a support comprising aluminum oxide, - Nickel, and - At least one promoter containing iron (Fe).

2. The process according to claim 1, wherein the catalyst further comprises at least one second promoter: - transition metal type promoters, in particular promoters containing cobalt (Co), manganese (Mn), copper (Cu) or silver (Ag); - lanthanide-type promoters, in particular promoters containing lanthanum (La), cerium (Ce) or gadolinium (Gd); - alkaline earth metal type accelerators, in particular accelerators containing barium (Ba); and / or - Alkali metal type accelerators, especially accelerators containing potassium (K).

3. The method according to claim 1 or 2, wherein: - the mass content of the promoter in the catalyst is between 0.1% and 40% by weight, preferably between 0.5% and 20% by weight, relative to the weight of the support; or The mass content of iron in the catalyst is between 0.1% and 40% by weight, preferably between 0.5% and 20% by weight, relative to the weight of the support.

4. The process according to any one of the preceding claims, wherein the catalyst comprises at least one second promoter comprising cobalt (Co).

5. A method according to any one of the preceding claims, wherein: - an iron content by mass of between 6% and 14% relative to the weight of the support; and / or The mass content of cobalt is between 0.1% and 4% relative to the weight of the support.

6. A process according to any one of the preceding claims, wherein the support is alumina.

7. A process according to any one of the preceding claims, wherein the mass content of nickel in the catalyst is between 0.1% and 50% by weight, relative to the weight of the support, preferably less than 20% by weight.

8. The method according to any of the preceding claims, wherein the cold plasma is generated by a dielectric barrier discharge (DBD).

9. A process according to any one of the preceding claims, wherein the catalyst comprises: - a support comprising aluminum oxide, - 0.1 to 50% by weight of nickel (weight % relative to the weight of the support), and - 0.1 wt% to 40 wt% of a promoter (wt% relative to the weight of the support), including an iron (Fe) promoter and at least one second promoter, the second promoter being selected from cobalt (Co), manganese (Mn), copper (Cu), silver (Ag), lanthanum (La), cerium (Ce), gadolinium (Gd), barium (Ba) and potassium (K).

10. A catalyst for converting a gas or gas mixture containing ammonia (NH3) into hydrogen (H2) and nitrogen (N2) according to the following reaction: The conversion is carried out in the presence of a cold plasma, characterized in that The catalyst contains: - a support comprising aluminum oxide, - Nickel, and - At least one promoter containing iron (Fe).

11. The catalyst according to claim 10, further comprising at least one second promoter: - transition metal type promoters, in particular promoters containing cobalt (Co), manganese (Mn), copper (Cu) or silver (Ag); - lanthanide-type promoters, in particular promoters containing lanthanum (La), cerium (Ce) or gadolinium (Gd); - alkaline earth metal type promoters, in particular barium (Ba); and / or - alkali metal type promoters, especially potassium (K).

12. The catalyst according to claim 10 or 11, wherein the mass content of the promoter in the catalyst is between 0.1 wt% and 40 wt%, preferably between 0.5 wt% and 20 wt%, relative to the weight of the carrier.

13. The catalyst according to any one of claims 10 to 12, comprising: - 0.1 to 50% by weight of nickel (wt% relative to the weight of the support), - 0.5 to 20 wt% of iron (Fe) (wt% relative to the weight of the support), and - 0.5 to 20 wt. % of one or more promoters (wt. % relative to the weight of the support) selected from the group consisting of cobalt (Co), manganese (Mn), copper (Cu), silver (Ag), lanthanum (La), cerium (Ce), gadolinium (Gd), barium (Ba) and potassium (K).

14. The catalyst according to any one of claims 10 to 13, comprising at least one second promoter comprising cobalt (Co), wherein: - an iron content by mass of between 6% and 14% relative to the weight of the support; and / or The mass content of cobalt is between 0.1% and 4% relative to the weight of the support.

15. Use of the catalyst according to any one of claims 10 to 14 for converting a gas or gas mixture containing ammonia (NH3), the conversion being carried out in a cold plasma, preferably a plasma generated by a dielectric barrier discharge (DBD).

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