Catalyzed method for combustion of dihydrogen

Abstract

The present invention relates to a catalyzed method for combustion of dihydrogen, in which dihydrogen forming a fuel is burned, said method being catalyzed by a catalyst comprising a catalytically active platinum (Pt) phase and an alumina (Al2O3) support, said catalyst being obtained by means of: - S1) providing an aluminum hydroxide (Al(OH)3) support; - S2) dispersing a platinum precursor in the support, the calcination decomposition of which forms the catalytically active phase; and - S3) treating the support in which the platinum precursor is dispersed on conclusion of step S2), comprising a drying sub-step S31) followed by a calcining sub-step S32) at a target temperature of between 250°C and 1000°C in order to jointly: -- convert the aluminum hydroxide (Al(OH)3) of the support to alumina (Al2O3); and -- obtain the catalytically active phase from the precursor dispersed in the support in step S2).

Description

[0001]DESCRIPTION Title of the invention: Method for manufacturing an optimized catalyst for maximized catalytic combustion of dihydrogen from room temperature TECHNICAL FIELD OF THE INVENTION The present invention relates to the field of catalytic combustion, and more particularly to a method for synthesizing a catalyst particularly suitable for equipping a domestic catalytic combustion device for the diffusion of perfume and / or active substances, for the destruction of odorous or non-odorous molecules, and / or for air purification. TECHNICAL BACKGROUND Certain devices for the diffusion of perfume and / or active substances, for the destruction of odorous or non-odorous molecules, and / or for air purification, operate on the so-called catalytic combustion of a perfumed solution based on alcohol derived from petrochemicals, commonly propan-2-ol also called isopropyl alcohol. Such devices, some of which are designated asthe term "catalytic lamps", generically comprise a bottle containing the solution, a wick immersed in the solution, and a catalytic head comprising a burner. The latter ensures the diffusion of the product by catalysis from the solution rising by capillarity along the wick. The catalytic reaction is a chemical oxidation reaction, without flame, which is facilitated at low temperature by the presence of the catalyst. In practice, the catalyst is a component that accelerates the speed of a chemical transformation and remains unchanged at the end of the reaction. The catalytic action results from the lowering of the activation energy level through which the transformation must be carried out. Generally speaking, a so-called impregnated catalyst comprises a catalytically active phase and a porous support, in which the active phase is diluted, which gives the whole the textural (specific surface area, porosity) and mechanical propertiessought. Although perfectly functional, the catalytic combustion of isopropyl alcohol generates carbon dioxide and volatile organic compounds which participate in the formation of ozone, which therefore contributes to the greenhouse effect. In a context of ecological transition, dihydrogen appears to be a particularly promising candidate to replace petroleum and its derivatives, and in particular to replace isopropyl alcohol in this case of use of catalytic lamp. Indeed, the combustion of dihydrogen does not as such emit volatile organic compounds, nor even carbon dioxide, in that it essentially produces water and heat in its expression: ^2 + ½ ^2 → ^2 ^ − 286 ^^ ^^^^^There are a number of research studies on catalytic reactors, catalysts and the identification of the different factors having an impact on the kinetics of catalytic combustion of dihydrogen, such as: - "Pt-impregnated catalysts on powdered SiC and other commercial supports for hydrogen combustion under oxidation conditions”, Jongho Kim a, Jianglong Yu, Soonho Lee, Arash Tahmasebi, Chung-Hwan Jeon, John Lucas, International Journal of Hydrogen RGY 46 (2021) 40073e40104, October 2021; - "Monolithic supports based on biomorphic SiC for the catalytic combustion of hydrogen", GM Arzac, J. Ramírez-Rico, Gutiérrez-Pardo, MC Jiménez de Haro, D. Hufschmidt, J. Martínez-Fernández, The Royal Society of Chemistry 2016, RSC Adv., 2016, 6, 66373. This work highlights the interest in forming catalysts whose active phase is based on platinum, as a noble reactive metal probably the most appropriate for reactions related to dihydrogen. Also, it is known from the literature, in particular from documents KR100522435 and KR100823929, to synthesize so-called Pt-alumina catalysts by means of a dispersion of platinum salt in alumina.The term alumina is used very generally to designate materials of the aluminum oxide type conventionally obtained by calcination of a precursor of the aluminum oxo-hydroxide or alumina monohydrate (AlOOH) type or of the aluminum hydroxide alumina trihydrate type also called alumina trihydrate (Al(OH)3]). Through testing, it appears that the catalysts prepared according to these methods known from the prior art do not make it possible to satisfactorily meet all the criteria of the specific specifications of a catalytic lamp, including in particular the major criteria of allowing: - the initiation of catalytic combustion in air at ambient temperature; and - a substantially total conversion of hydrogen at 100°C. Following the development of Pt-alumina type catalysts, the invention aims to propose a process for synthesizing a catalyst making it possible to ensure maximum catalytic activity at 100°C with initiation in air at temperatureambient to be transposable to a catalytic lamp, or other domestic catalytic combustion devices for the diffusion of perfume and / or active substances, for the destruction of odorous or non-odorous molecules, and / or for air purification. Such a catalyst can also be used for other applications such as domestic heating. DISCLOSURE OF THE INVENTION To this end, the subject of the invention is a method for the combustion of dihydrogen, in which dihydrogen forming fuel is burned by being catalyzed by at least one catalyst, the combustion method comprising: - the provision of at least one catalyst comprising a catalytically active phase of platinum (Pt) and an alumina (Al2O3) support, and - the supply of dihydrogen forming fuel in the vicinity of said at least one catalyst to be burned there; in which said at least one catalyst used is obtained at the end of the successive steps of: - S1) provision of a hydroxide supportof aluminum (Al(OH)3); - S2) dispersion in said support of a platinum precursor, the decomposition of which by calcination forms the catalytically active phase; and - S3) treatment of the support in which the platinum precursor is dispersed at the end of step S2), comprising a sub-step S31) of drying followed by a sub-step S32) of calcination at a target temperature of between 250°C and 1000°C to jointly: -- transform the aluminum hydroxide (Al(OH)3) of the support into alumina (Al2O3); and -- obtain the catalytically active phase from the precursor dispersed in the support with phase S2). The invention also relates to a process thus defined, in which the dihydrogen forming fuel is burned from room temperature. The invention also relates to a process thus defined, in which the catalyst used has a platinum (Pt) content of between 0.3 and 1% by weight. The invention also relates to a method thus defined, in which thecatalyst used is integrated into a device for the diffusion of perfume and / or active substances, for the destruction of odorous or non-odorous molecules, and / or for air purification. The invention also relates to a process thus defined, in which the aluminum hydroxide constituting the support provided in step S1) is Bayerite (Al(OH)3). The invention also relates to a process thus defined, in which the calcination temperature in sub-step S32) of the Bayerite (Al(OH)3) support is between 550°C and 650°C. The invention also relates to a process thus defined, in which the aluminum hydroxide constituting the support is Gibbsite (Al(OH)3). The invention also relates to a process thus defined, in which the calcination temperature in sub-step S32) of the Gibbsite support is set at substantially 550°C. The invention also relates to a method thus defined, in which: - sub-step S31) of drying the impregnated support includesfreezing at a temperature of -18°C for 12 hours followed by freeze-drying for 12 hours; and - sub-step S32) of calcining the support is ensured by a gradual increase in temperature until the target temperature is reached, followed by maintenance at the target temperature for two hours. The invention also relates to a method thus defined, in which step S2) of dispersing the precursor in the support provided in step S1) is carried out by impregnation or by exchange. The invention also relates to a method thus defined, in which the platinum precursor used in step S2) is a solution of hexachloroplatinic acid (H2PtCl6) or a solution of tetraammineplatinum dichloride (Pt(NH3)4Cl2). BRIEF DESCRIPTION OF THE DRAWINGS Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which one will refer to the appended drawings in which: – [Fig.1] is aflowchart of the process according to the invention; – [Fig.2] illustrates the results of catalytic activity between room temperature and 100°C of a catalyst (Pt / Bayerite)-550°C obtained by impregnation of 0.5%Pt on Bayerite followed by calcination at 550°C in accordance with the process according to the invention, and of a control catalyst (Pt / Al2O3exBayerite)-550°C obtained by calcination at 550°C of an alumina support derived from Bayerite and impregnated with 0.5%Pt according to a process different from that of the invention; – [Fig.3] illustrates the catalytic activity results of three batches of catalysts (0.5Pt / Bayerite)-550°C obtained by impregnation of 0.5%Pt on Bayerite followed by calcination at 550°C according to the process according to the invention; – [Fig.4] illustrates the catalytic activity results of catalysts (0.5Pt / Al2O3exBayerite)-550°C and (0.5Pt / Al2O3 exBayerite)-550°C bis obtained by calcination at 550°C of alumina supports derived from Bayerite and impregnated with 0.5%Pt according to a processdifferent from that of the invention; – [Fig.5] illustrates the results by dark field transmission electron microscopy (ADF STEM) of a catalyst (0.5Pt / Bayerite)-550°C obtained by impregnation of 0.5%Pt on Bayerite followed by calcination respectively at 550°C in accordance with the process according to the invention; – [Fig.6] illustrates the results by dark field transmission electron microscopy (ADF STEM) of a catalyst (0.5Pt / Al2O3 exBayerite)-550°C obtained by calcination at 550°C of an alumina support derived from Bayerite and is impregnated with 0.5%Pt according to a process different from that of the invention; – [Fig.7] illustrates the catalytic activity results of four catalysts (0.3%Pt / Bayerite)-550°C, (0.5%Pt / Bayerite)-550°C, (0.8%Pt / Bayerite)-550°C and (1%Pt / Bayerite)-550°C obtained by impregnation of respectively 0.3%, 0.5%, 0.8% and 1% by weight content of platinum on Bayerite followed by calcination at 550°C in accordance with the process according to the invention; – [Fig.8]illustrates the catalytic activity results of eight catalysts (0.5Pt / Bayerite)-T°C obtained by impregnation of 0.5%Pt on Bayerite by the incipient humidity impregnation method followed by calcination at different temperatures between 250 and 1000°C; – [Fig.9] illustrates the catalytic activity results of six catalysts manufactured by dispersion of platinum in Bayerite (Al(OH)3) by the anion exchange method before calcination at 550°C; – [Fig.10] illustrates the catalytic activity results of a catalyst (0.5Pt / Bayerite)-550°C: H2PtCl6 obtained by impregnation of the Bayerite support with a solution of hexachloroplatinic acid H2PtCl6, and of a catalyst (0.5Pt / Bayerite)-550°C: Pt(NH3)4Cl2 obtained by impregnation of the Bayerite support with a solution of tetraammineplatinum dichloride Pt(NH3)4Cl2; – [Fig.11] illustrates the catalytic activity results of a catalyst (0.5Pt / Gibbsite)-550°C obtained by impregnation of 0.5%Pt on Gibbsitefollowed by calcination at 550°C in accordance with the process according to the invention, and a catalyst (0.5Pt / Al2O3 exGibbsite)-550°C obtained by calcination at 550°C of an alumina support derived from Gibbsite and impregnated with 0.5%Pt according to a process different from that of the invention; – [Fig.12] illustrates the catalytic activity results of a catalyst (0.5Pt / Boehmite)-550°C obtained by impregnation of 0.5%Pt on Boehmite followed by calcination at 550°C, and of a catalyst (0.5Pt / Al2O3 exBoehmite)-550°C obtained by calcination at 550°C of an alumina support derived from Boehmite and impregnated with 0.5%Pt according to a process different from that of the invention; – [Fig.13] presents photos: 1) of Bayerite, Gibbsite and Boehmite; 2) catalysts (0.5Pt / Bayerite) -550°C, (0.5Pt / Gibbsite) -550°C and (0.5Pt / Gibbsite) -550°C obtained by impregnation of 0.5%Pt on Bayerite, Gibbsite and Boehmite respectively, followed by calcination at 550°C; 3) aluminas Al 2 O 3 exBayerite , Al 2 O3 exGibbsite et al. 2 Or 3 exBoehmiteobtained by calcination at 550°C of Bayerite, Gibsite and Boehmite respectively; and 4) of catalysts (0.5Pt / Al2O3 exBayerite) -550°C, (0.5Pt / Al2O3 exGibbsite) -550°C and (0.5Pt / Al2O3 exBoehmite) -550°C obtained after impregnation of 0.5%Pt on alumina Al2O3 exBayerite, Al2O3 exGibbsite and Al2O3 exBoehmite respectively, followed by calcination at 550°C. DETAILED DESCRIPTION OF THE INVENTION Within the scope of the invention, it is aimed to propose a catalyst active in the combustion of dihydrogen from room temperature and providing substantially complete combustion at 100°C, so as to authorize its use in a catalytic lamp for safe domestic use. It is known from the state of the art to form Pt-Alumina type catalysts, namely catalysts whose active phase is platinum and the support is formed from transition alumina, to ensure catalytic combustion of dihydrogen.These Pt-Alumina catalysts known from the state of the art are formed by impregnation of a transition alumina (Al2O3) support with a solution of hexachloroplatinic acid (H2PtCl6), called platinum precursor salt, followed by drying and calcination steps. In practice, in solution, hexachloroplatinic acid (H2PtCl6) is dissociated into H protons. + and anions [PtCl6 2-], and the anions attach to the alumina dispersed in this acidic solution, the surface of the alumina being positively charged at acidic pH. The chlorine (Cl) is then partially or completely eliminated by means of calcination which decomposes the PtCl6 species, thus obtaining the Pt-Alumina catalyst. So-called transition alumina (Al2O3), also called aluminum oxide, is a crystalline structure resulting from the dehydration of precursors of the alumina hydrate type: aluminum hydroxides of formula Al(OH)3 and aluminum oxo-hydroxides AlO(OH). In practice, alumina (Al2O3) is metastable, that is, it varies irreversibly according to the dehydration of the precursor until reaching its final thermodynamically stable form, called α-alumina.One of the most widely used forms of alumina used to form the support before its impregnation with platinum salt is the so-called gamma alumina (γ-Al2O3) obtained by calcination of Boehmite (AlOOH) which is an aluminum oxo-hydroxide. Although these Pt-alumina catalysts are recognized as particularly suitable for the catalytic combustion of dihydrogen, their action at room temperature is insufficient while their maximum activity is observed at temperatures significantly above 100°C.This results in a risk that the residual part of the unconsumed dihydrogen, from room temperature up to 100°C, accumulates and leads to the formation of explosive combustible mixtures, which is not admissible from an operational safety point of view for equipping a catalytic lamp in a domestic application. The invention is part of a study aimed at evaluating the opportunities for improving Pt-alumina type catalysts to meet the above-mentioned criteria, in particular by carrying out variations in the synthesis process.It was surprisingly observed during this study that dispersing a platinum precursor on aluminum hydroxide (Al(OH)3), before calcining to obtain both alumina (Al2O3) from aluminum hydroxide (Al(OH)3) and platinum (Pt) from the platinum precursor, makes it possible to obtain Pt-alumina catalysts whose response in catalytic combustion of dihydrogen is significantly improved. In particular, the effectiveness of the process according to the invention has been demonstrated in the context of the invention regardless of the polymorph, Bayerite and Gibbsite, of aluminum hydroxide (Al(OH)3 considered.The process for manufacturing a Pt-alumina type catalyst thus defined in the context of the invention requires overall: - a step S1) of providing an aluminum hydroxide (Al(OH)3) support; - a step S2) of dispersing a platinum precursor in said support; - a step S3) of treating the support in which the platinum precursor is dispersed at the end of step S2), comprising a sub-step S31) of drying followed by a sub-step S32) of calcination at a temperature between 250° and 1000°C. The process according to the invention is shown diagrammatically in Figure 1. It is advantageously recommended that the calcination applied to the impregnated Bayerite or Gibbsite support in step c) be carried out at a temperature of 550° or 650°C to obtain the most optimized catalyst.As understood, the major feature of the invention lies in the use of an aluminum hydroxide as a support to which a platinum precursor is added before co-calcining both the support and the platinum precursor embedded in this support to obtain a Pt-alumina catalyst which is particularly efficient from room temperature. In the following, examples of test results on the basis of which the process according to the invention was formulated will be presented. Example 1 This first example corresponds to a comparative analysis of catalytic activity obtained between: - a Pt-alumina catalyst with a platinum content by weight of the order of 0.5%, synthesized in accordance with the process according to the invention, by impregnating the platinum salt directly onto a Bayerite (Al(OH)3) support as aluminum hydroxide, the calcination of which results in the formation of alumina (Al2O3); and - a so-called "control" Pt-Alumina catalyst with a platinum content by weight of the order of 0.5%, which is manufactured in the manner recommended in the state of the art, namely by impregnating the platinum salt onto the alumina (Al2O3) obtained in this case after the calcination of the Bayerite (Al(OH)3). In the context of this first comparative study, two Pt-alumina catalysts were manufactured.Test matrix – example 1 Among these two catalysts listed in table 1 below, we distinguish: - a first catalyst referenced (Pt / Bayerite)-550°C manufactured in accordance with the process according to the invention by directly impregnating Bayerite (Al(OH)3) with the platinum salt, followed by calcination at 550°C transforming Bayerite (Al(OH)3) into alumina (Al2O3); and - a second catalyst referenced (Pt / Al2O3 exBayerite-550) -550°C not in accordance with the invention, manufactured by calcining Bayerite (Al(OH)3) at 550°C to transform it into alumina (Al2O3) before being impregnated with the platinum salt; followed by calcination at 550°C. [Table 1] SUPPORT ACTIVE PHASE CATALYST NOMENCLATUR E Nature / Nature Content Treatment (Pt / (support))-T°C Temperature (%wt) post- calcination impregnation Bayerite Calcination at (Pt / Bayerite)- Pt 0.5 (Al(OH)3) 550 °C 550°C. Alumina (Al2O3) (ex- (Pt / Al2O3 exBayerite- Bayerite 550) -550°C calcined at 550°C) Production – example 1 In detail, each catalyst was produced in a quantity of 5g on the same base of commercial Bayerite (Al(OH)3) ((Al(OH)3 - PURAL BT, SASOL Chemicals) and hexachloroplatinic acid (H2PtCl6) in aqueous solution containing 1.45% by weight of platinum. For the preparation of the catalyst (Pt / Al2O3 exBayerite-550) -550°C called "control", i.e. not in accordance with the invention, a calcination at 550°C of the Bayerite (Al(OH)3) was first carried out to obtain the transition alumina (Al2O3) intended to serve as an impregnation support. This support is designated by Al2O3 exBayerite-550. This calcination of Bayerite (Al(OH)3) before impregnation in the context of the production of the control catalyst was carried out in hot air, at 550°C, remaining 2 hours at maximum temperature in a muffle furnace with a heating rate of 5°C / min.Once the alumina was obtained, 5g was taken to form the corresponding Al2O3 exBayerite-550 support. For the preparation of the (Pt / Bayerite)-550°C catalyst, 6.68g of Bayerite (Al(OH)3) was used as the impregnation support. This particularity arises from the fact that Bayerite is subject to a mass variation during its calcination after impregnation due to water losses by dehydroxylation. The value of 6.68g of Bayerite was determined on the basis of a mass loss quantification, as follows: ^%. ^^^^^^^ ^^^^^^^^^^^^^ ^^^^^^^^ ^^^^^= ^^^^^^^^ × 100 ^ m^^^^^^^ = ^^^^%^^^^^ × 100 Once all the impregnation supports were produced, they underwent a so-called "incipient wetness" impregnation. This type of impregnation consists of bringing the support into contact with an aqueous solution containing hexachloroplatinic acid (H2PtCl6) in a quantity slightly greater than the pore volume of the support in order to fill all the available pores of this support. This technique thus required first determining for each of the supports the quantity of aqueous solution containing hexachloroplatinic acid (H 2 PtCl 6) to be produced to achieve a Pt impregnation of the order of 0.5% on this basis: For 5g of catalyst at 0.5% by weight of platinum to be formed, the following were thus produced: - 6.23g of aqueous solution of hexachloroplatinic acid containing 0.025g of platinum to impregnate the support of 6.68g of Bayerite (Al(OH)3) associated with the synthesis of the catalyst (Pt / Bayerite)-550°C. - 7.42g of aqueous solution of hexachloroplatinic acid (H2PtCl6) containing 0.025g of platinum to impregnate the alumina support resulting from the calcination of 5g of Bayerite (Al(OH)3), in order to prepare the synthesis of the catalyst (Pt / Al2O3 exBayerite-550) -550°C. The supports were then each placed in a Pyrex flask and impregnated drop by drop with the corresponding aqueous hexachloroplatinic acid solution, before being placed in a rotary evaporator and left stirring for two hours at atmospheric pressure and room temperature.The supports now impregnated with the aqueous solution of hexachloroplatinic acid were then dried and calcined. The drying step was carried out by freezing the impregnated supports at a temperature of -18°C for 12 hours, followed by freeze-drying the solid mass obtained for 12 hours to achieve complete drying. The impregnated and dry supports were finally calcined under hot air at 550°C in a muffle furnace with a heating rate of 5°C / min, remaining at maximum temperature for two hours. Validation of the composition and catalytic tests – example 1 With reference to Table 2, the percentage of platinum deposited on the different supports was verified by inductively coupled plasma spectrometry, commonly referred to as "ICP". [Table 2]. Pt content Pt content Catalyst theoretical (%wt) actual (%wt). -550°C 0.5 0.51(Pt / Al2O3 exBayerite-550) -550°C 0.5 0.47As observed, the effective platinum content deposited by incipient wetness impregnation varies between 0.47 and 0.51 wt%, which is very close to the theoretical target content. On this basis, the reproducibility of this incipient wetness impregnation method is validated. It follows that the behavior of catalysts manufactured according to the manufacturing process can be validly compared with that of catalysts manufactured in the usual way, based on the same common denominator {Bayerite - Pt content - calcination temperature}.The catalytic combustion performances of dihydrogen were evaluated under the same standard operating conditions as follows: - a quantity of 50 mg of each catalyst is diluted in 5 g of silicon carbide (SiC) and then loaded into a fixed-bed Pyrex© glass tubular reactor operating at atmospheric pressure; - the reactor is subjected for 30 minutes to a pretreatment at room temperature (20-22°C) under a synthetic air flow of 50 mL / min; - the catalytic activity is monitored at room temperature (20-22°C) for 30 minutes and for 1 hour of heating from room temperature to 100°C under a gas flow comprising synthetic air and 2% dihydrogen. The monitoring of the catalytic conversion of hydrogen was based on a gas chromatographic analysis using a TCD detector, for "Thermal Conductivity Detector".The hydrogen conversion rate is expressed as the ratio between the difference in hydrogen concentrations before and after the reaction and the hydrogen concentration before the reaction. The hydrogen concentration before the start of the reaction was measured in particular via a bypass circuit of the catalytic bed during the pretreatment period of the catalytic bed under air at the start of the test. Analysis of the results – example 1 Figure 2, which compiles the catalytic activity results of the two catalysts manufactured, highlights that the catalyst (Pt / bayerite) - 550°C, namely the catalyst based on 0.5% Pt impregnated on Bayerite and then calcined at 550°C in accordance with the process according to the invention, is active in catalytic combustion of dihydrogen from room temperature, with a stable conversion around 37%.Also, the hydrogen conversion of this catalyst increases progressively with the increase in the furnace temperature: of the order of 50% dihydrogen conversion is obtained at 40°C and more than 90% from 65°C. Conversely, it appears that the control catalyst (Pt / Al2O3 exBayerite-550) -550°C, whose manufacture differs only from that of the catalyst (Pt / bayerite) -550°C in that the support was calcined before platinum impregnation, is inactive at room temperature and remains so up to 75°C. At 97°C, the dihydrogen conversion by this catalyst (Pt / Al2O3 exBayerite-550) -550°C remains below 20%.Figure 2 thus shows that the Pt / alumina (Al2O3) type catalyst manufactured from Bayerite impregnated with 0.5% platinum and then calcined at 550°C, in accordance with the process according to the invention, has a substantial gain in performance in catalytic combustion compared to a Pt / alumina (Al2O3) catalyst of the same type but whose Bayerite is calcined before impregnation. Example 2 To verify the repeatability of the catalytic activity results of the (Pt / bayerite) -550°C catalyst demonstrated in Example 1, satisfying in particular the criteria sought within the framework of the invention, three other batches of (Pt / bayerite) -550°C catalysts were manufactured.Manufacturing – Example 2 These catalysts, designated Batch 1, Batch 2 and Batch 3, were manufactured in exactly the same way as described in Example 1, namely by: - ​​adding 6.68 g of Bayerite (Al(OH)3) to form each impregnation support; - impregnation by nascent humidity of these impregnation supports with 6.23 g of aqueous solution of hexachloroplatinic acid (H2PtCl6) containing 0.025 g of platinum; then - drying followed by calcination at 550°C of the impregnated supports. Catalytic tests and analysis of results – example 2 The reaction performance in catalytic combustion of dihydrogen of batches 1, 2 and 3 was evaluated under the same operating conditions as in example 1. As visible in figure 3, the catalytic activity results of batches 1, 2 and 3 are substantially the same and superimposable on those obtained on the basis of the catalyst (Pt / bayerite) -550°C of example 1.It can be observed in particular that the (Pt / bayerite) - 550°C catalysts of batches 1, 2 and 3: - convert dihydrogen at room temperature at a rate of 38% to 43%; - achieve 50% conversion of dihydrogen around 40°C; and - ensure total conversion of dihydrogen from 90°C. The results obtained in the context of this example 2 thus validate the reproducibility of the synthesis process according to the invention and the performances that they can be granted by impregnation on Bayerite. Example 3 On the basis of example 2, uniformity of the catalytic performances of the (Pt / bayerite) -550°C type catalysts with a content of 0.5% platinum manufactured in accordance with the process according to the invention was observed. This example 3 aims to ensure a real gain in performance of these catalysts (Pt / bayerite) -550°C manufactured using the process according to the invention compared to catalysts formed in the usual manner.In this respect, another so-called "bis" catalyst of the (Pt / Al2O3 exBayerite-550) -550°C type not in accordance with the invention was manufactured in the same way as in Example 1 and its catalytic activity was evaluated under the same operating conditions. As can be seen in Figure 4, which compiles the test results of the (Pt / Al2O3 exBayerite-550) -550°C bis catalyst with those of the (Pt / Al2O3 exBayerite-550) -550°C catalyst of Example 1, these catalysts not in accordance with the invention are indeed inactive up to a temperature of 75°C. At 97°C the hydrogen conversion is less than 20% in the presence of (0.5% Pt / Al2O3exBayerite)-550°C, while it is less than 10% in the presence of (0.5% Pt / Al2O3exBayerite)-550°C-bis. Example 3 thus validates the observations made in Example 1, and confirms the real gain of the synthesis process according to the invention.Example 4 With reference to Figures 5 and 6, the morphology differences between a (Pt / bayerite)-550°C catalyst in accordance with the invention and a non-compliant (Pt / Al2O3exBayerite)-550°C catalyst were assessed by Dark Field Transmission Electron Microscopy (ADF STEM). The (Pt / bayerite)-550°C catalyst is characterized by polydisperse Pt particle sizes with a significant population of nanoparticles between 5 and 20 nm, small (1-2 nm) metal nanoparticles (NPs) and isolated platinum atoms (ions) / clusters. The control catalyst (Pt / Al. 2 O 3 exBayerite)-550°C, synthesized in the usual way, presents a homogeneous dispersion of platinum particles with the presence of only two populations, small (1-2nm) metallic nanoparticles (NPs) and isolated atoms (ions) / clusters. The formation of a significant population of the largest platinum nanoparticles, between 5 and 20 nm, observed on the (Pt / bayerite) catalyst -550°C suggests a sintering of the platinum particles made possible by the water generated during calcination, by dehydroxylation of the support. Example 5 In order to assess the robustness of the catalyst synthesis process according to the invention, the behavior of the (Pt / bayerite) type catalysts was evaluated by modifying the mass content of platinum in the catalytic phase. The objective of this analysis is to verify that the recorded performances of the catalysts manufactured in accordance with the process according to the invention are not limited to the case for which the impregnated platinum content is fixed at 0.5% by weight.In this regard, four catalysts were manufactured and then tested in the same way as in Example 1, except that they differ from each other in their platinum content. In more detail, we distinguish: - a catalyst (0.3% Pt / bayerite)-550°C containing 0.3% platinum; - a catalyst (0.5% Pt / bayerite)-550°C containing 0.5% platinum; - a catalyst (0.8% Pt / bayerite)-550°C containing 0.8% platinum; and - a catalyst (1% Pt / bayerite)-550°C containing 1% platinum. With reference to Figure 7, the results show that the more the platinum content is increased, the more the conversion rates are improved. In detail, the hydrogen conversion at room temperature recorded is: - of the order of 20-30% for the catalyst (0.3%Pt / bayerite)-550°C; - of the order of 30-40% for the catalyst (0.5%Pt / bayerite)-550°C; - of the order of 55-65% for the catalyst (0.8%Pt / bayerite)-550°C; and - of the order of 65-85% for the catalyst (1%Pt / bayerite)-550°C.It is thus clear from this example that the higher the mass content of platinum in the catalytic phase, the greater the activity in catalytic combustion of dihydrogen. Since the performance of the catalysts manufactured by the process according to the invention logically aligns with the platinum content, the observations made in Example 1 do not therefore result from a particular exception. It follows that the process according to the invention is not strictly limited to forming Pt / alumina type catalysts from Bayerite loaded with 0.5% platinum by weight. In other words, the platinum content is not a limiting factor of the process according to the invention. Example 6 In this example, the aim is to quantify the influence of the calcination temperature on the activity of the catalysts obtained by the process according to the invention.Concretely, it is a question of determining a range of calcination temperatures for which the process according to the invention allows the production of catalysts active in catalytic combustion of dihydrogen from room temperature. Test matrix and manufacture – example 6 On this basis, eight (Pt / Bayerite)-T°C catalysts were manufactured in accordance with the process according to the invention by impregnating Bayerite (Al(OH)3) with the aqueous solution of hexachloroplatinic acid (H2PtCl6), to obtain a platinum content of 0.5% by weight, before calcining at distinct temperatures T°C between 250°C and 1000°C, as follows: [Table 3] S. UPPORT PHASECATALYST NOMENCLATURE ACTIVE Type Type Content Post-treatment (Pt content / (support))-T°C (% wt) impregnation Calcination at (0.5% Pt / bayerite)-250°C 250 °C Calcination at (0.5% Pt / bayerite)-350°C 350 °C Calcination at (0.5% Pt / bayerite)-450°C 450 °C Calcination at (0.5% Pt / bayerite)-550°C Bayerite 550 °C Pt 0.5 (Al(OH)3) Calcination at (0.5% Pt / bayerite)-650°C 650 °C Calcination at (0.5% Pt / bayerite)-750°C 750 °C Calcination at (0.5% Pt / bayerite)-850°C 850 °C Calcination at (0.5% Pt / bayerite)-1000°C 1000 °C Catalytic tests and analysis of results – example 6 Once these catalysts (Pt / Bayerite)-T°C were manufactured, their catalytic activities were measured while respecting the operating conditions of example 1.With reference to Figure 8, it is observed that: - all the (Pt / Bayerite)-T°C catalysts manufactured are active from room temperature; - the conversion to dihydrogen is greater than 20% at room temperature for the catalysts whose calcination temperature is in the range [350°C-850°C]; - the (Pt / Bayerite)-250°C and (Pt / Bayerite)-1000°C catalysts, whose calcination temperatures correspond to the extremum values ​​of the batch of (Pt / Bayerite)-T°C catalysts manufactured, are the least efficient, displaying conversion rates of the order of 10% at room temperature; - the catalytic activity is optimal, with a dihydrogen conversion equal to or greater than 40%, following calcination at 550°C or 650°C.In view of the above, it appears that the process according to the invention guarantees the manufacture of high-performance (Pt / Bayerite)-T°C type catalysts from room temperature regardless of the calcination temperature T chosen in the range [250°C-1000°C]. It is thus demonstrated that the process according to the invention is not limited to the calcination temperature T value of 550°C of Example 1. Calcination between 550° and 650°C will be chosen to obtain the highest performance. Example 7 Examples 1 to 6 made it possible to validate the performance of Pt-Alumina type catalysts manufactured in accordance with the process according to the invention by means of impregnation with nascent humidity of a Bayerite support with a solution of hexachloroplatinic acid (H2PtCl6).In this example 7, the aim is to quantify the influence of the dispersion method in the Bayerite support of the platinum precursor, and more specifically to verify whether the process according to the invention is limited or not to the incipient wetness impregnation method of hexachloroplatinic acid (H2PtCl6). Test matrix – example 7 In the context of this example, six catalysts were manufactured by dispersing hexachloroplatinic acid (H2PtCl6) in Bayerite (Al(OH)3) by the anion exchange method before calcination at 550°C. The catalysts, each manufactured with a distinct platinum content, are referenced (x%Pt / bayerite)-550 where x is the mass content of platinum (determined by ICP) as follows: [Table 4] S. UPPORT PHASECATALYST NOMENCLATURE ACTIVE Type Type Content Post-treatment (Pt content / (support))-T°C (% wt) dispersion by exchange 0.22 (0.22% Pt / bayerite)-550°C 0.41 (0.41% Pt / bayerite)-550°C 0.45 (0.45% Pt / bayerite)-550°C Bayerite Calcination at Pt (Al(OH)3) 0.48 550 °C (0.48% Pt / bayerite)-550°C 0.49 (0.49% Pt / bayerite)-550°C 0.59 (0.59% Pt / bayerite)-550°C Fabrication – example 7 Synthesis by anion exchange consists of suspending the bayerite support in an aqueous solution of the platinum salt H2PtCl6. In aqueous solution, the salt is completely dissociated (2 H + , PtCl6 2- ). The suspension is left stirring for a set period of time to allow the anionic species PtCl6 2- to exchange with the surface of the bayerite. The suspended solid is then separated by filtration; this solid corresponds to the bayerite enriched with PtCl6 species 2-retained on its surface. Several exchange preparations are carried out using hexachloroplatinic acid solutions of increasing concentrations so as to vary the quantities of platinum species retained and to reach saturation of the surface. The catalysts were then dried by freeze-drying and calcined at 550°C, in the same way as in the manufacture of the catalysts prepared by impregnation in Example 1. In detail, each catalyst was manufactured in a quantity of 3g on the same base of commercial Bayerite (Al(OH)3) ((Al(OH)3 - PURAL BT, SASOL Chemicals) and hexachloroplatinic acid (H2PtCl6). The initial mass of bayerite used for the exchange was taken in excess in order to obtain the desired quantity of catalyst at the end of the calcination step. Indeed, the mass loss of the support during calcination at 550°C is 25.2% (water losses by dehydroxylation during calcination).The bayerite support, suspended in an aqueous solution of hexachloroplatinic acid, is left stirring in a rotary evaporator for two hours at atmospheric pressure and room temperature to allow the exchange between the bayerite and the platinum species in solution. To achieve the desired platinum content for each of the catalysts, 20g of hexachloroplatinic acid solutions of increasing concentrations were prepared, containing: - 0.0075g of platinum to obtain the 0.22%Ptech / bayerite-550 catalyst; - 0.015g of platinum for the 0.41%Ptech / bayerite-550 catalyst; - 0.0225g of platinum for the 0.45%Ptech / bayerite-550 catalyst - 0.03g of platinum for the 0.48%Ptech / bayerite-550 catalyst; - 0.0375g of platinum for the 0.49%Ptech / bayerite-550 catalyst; and - 0.06g of platinum for the 0.59%Ptech / bayerite-550 catalyst.The supports thus enriched in platinum were then dried and calcined following the same protocol as that described in Example 1. The wet solids, separated by centrifugation, were frozen at a temperature of -18°C for 12 hours, before being freeze-dried for 12 hours to achieve complete drying, then calcined. Calcination was carried out under hot air at 550°C in a muffle furnace with a heating rate of 5°C / min, remaining two hours at maximum temperature. Catalytic tests and analysis of results – example 7 The performances in catalytic combustion of dihydrogen were evaluated under the same standard operating conditions as in example 1, and compiled in figure 9. Figure 9 shows that the catalysts prepared by exchange are active in catalytic combustion of dihydrogen at room temperature, in the order of 5% to 10% conversion, for a platinum content greater than 0.4%.A dihydrogen conversion of 50% is notably achieved for these catalysts when the furnace temperature reaches 70°C-80°C. On this basis, it is thus justified to conclude that the process according to the invention is not limited to the technique used to disperse the platinum salt (H2PtCl6), as a platinum precursor, in the Bayerite support. Example 8 The previous examples have made it possible to validate the performance of the Pt-Alumina type catalysts manufactured in accordance with the process according to the invention using different dispersion techniques of the same platinum precursor, namely hexachloroplatinic acid (H2PtCl6). In this example 8, it is aimed to verify whether or not the process is constrained to the use of hexachloroplatinic acid (H2PtCl6), and more generally to a specific nature of platinum precursor.Test matrix – example 8 In this example, two catalysts were manufactured following the same protocol, except that two different platinum precursors were used, each associated with a corresponding catalyst: hexachloroplatinic acid (H2PtCl6) and tetraammineplatinum dichloride (Pt(NH. 3 ) 4 Cl 2). Among these two catalysts listed in Table 5 below, we distinguish: - a first catalyst referenced (0.5%Pt / Bayerite)-550°C: H2PtCl6 manufactured by impregnation with nascent humidity directly of Bayerite (Al(OH)3) with a solution of hexachloroplatinic acid, followed by calcination at 550°C to jointly obtain alumina (Al2O3) from Bayerite (Al(OH)3) and the active phase in platinum from hexachloroplatinic acid; and - a second catalyst referenced (0.5%Pt / Bayerite)-550°C: Pt(NH3)4Cl2 manufactured by incipient humidity impregnation directly of Bayerite (Al(OH)3) with an aqueous solution of Tetraammineplatinum Dichloride (Pt(NH3)4Cl2), followed by calcination at 550°C to jointly obtain alumina (Al2O3) from Bayerite (Al(OH)3) and the active platinum phase from Tetraammineplatinum Dichloride.[Table 5] SUPPORT ACTIVE PHASE CATALYST NOMENCLATURENature NatureContent Treatment (%Pt / (support))- (Precursor) (%wt) post- T°C: precursor impregnation (0.5%Pt / Bayerite)- Pt (H2PtCl6) 550°C: H2PtCl6 Bayerite Calcination at 0.5 (Al(OH)3) Pt 550 °C (0.5%Pt / Bayerite)- (Pt. 4Cl2) 550°C: Pt(NH3)4Cl2 Fabrication – Example 8 In the case of the catalyst (0.5%Pt / Bayerite)-550°C: H2PtCl6, the preparation of its support and its impregnation were carried out in the same way as described in Example 1 in order to obtain 5g of catalyst. Regarding the preparation of 5g of the catalyst (0.5%Pt / Bayerite)-550°C: Pt(NH3)4Cl2, 6.68g of commercial Bayerite (PURAL BT, SASOL Chemicals) were used as inorganic support. The initial mass of Bayerite used for impregnation was taken in excess in order to obtain the desired quantity of catalyst at the end of the synthesis. Indeed, the mass loss in support during calcination at 550°C is 25.2% (water losses by dehydroxylation during calcination, after impregnation). For the impregnation of the support, 6.23 g of an aqueous solution of Pt(NH3)4Cl2 containing 0.025 g of platinum was prepared.The impregnation of the support with the solution was carried out drop by drop in a Pyrex flask, before being placed in a rotary evaporator and left stirring for two hours at atmospheric pressure and room temperature. The now impregnated supports were then dried and then calcined in the same way as in the case of Example 1, namely: - freezing them at a temperature of -18°C for 12 hours before freeze-drying them for 12 hours until completely dry; then - calcining them in air for 2 hours at 550°C in a muffle furnace using a heating rate of 5°C / min. Catalytic tests and analysis of results – Example 8 The performances in catalytic combustion of dihydrogen were evaluated under the same standard operating conditions as in Example 1, and compiled in Figure 10.Figure 10 shows that both catalysts are very active in the catalytic combustion of dihydrogen from room temperature, with a conversion greater than 40%. On this basis, it is understood that the process according to the invention makes it possible to obtain Pt-Alumina catalysts that are efficient in the catalytic combustion of dihydrogen from this temperature, regardless of the nature of the Pt precursor dispersed in the Bayerite support. Examples 1 to 8 thus made it possible to validate the performance of the Pt-Alumina catalysts manufactured in accordance with the process according to the invention by dispersing a platinum precursor in a Bayerite support which is an aluminum hydroxide. In the following examples 9 and 10, it is intended to evaluate whether the process is applicable for other alumina hydrates, precursors of the Alumina-based support of the aluminum hydroxide or aluminum oxo-hydroxide type.Example 9 This example 9 aims to verify whether a generalization of the process to any form of aluminum hydroxide (Al(OH)3) is possible. Test matrix – example 9 In this sense, this example is based on a comparative analysis of catalytic activities obtained between two Pt-Alumina catalysts manufactured from Gibbsite as listed in Table 6, including: - a Pt-Alumina catalyst referenced (Pt / Gibbsite)-550°C, with a platinum content by weight of the order of 0.5%, synthesized in accordance with the process according to the invention by directly impregnating the platinum salt onto a Gibbsite (Al(OH)3) support, followed by calcination at 550°C transforming the Gibbsite (Al(OH)3) into alumina (Al2O3); and - a “control” Pt-Alumina catalyst referenced (Pt / Al2O3 exGibbsite 550°C), with a platinum content of around 0.5%, manufactured in the manner recommended in the state of the art, namely by impregnating the platinum salt on the alumina obtained after the calcination of Gibbsite (Al(OH)3) at 550°C. [Table 6] SUPPORT PHASE CATALYST NOMENCLATURE ACTIVE Nature / Nature ContentPost-treatment (Pt / (support))-T°C Temperature r impregnation of calcination (%wt ) Gibbsite (Pt / Gibbsite)- (Al(OH)3) 550°C Al2O3 (ex- Calcination at Pt 0.5 550 °C gibbsite (Pt / Al2O3 exGibbsite- calcined at 550) -550°C 550°C) Fabrication – example 9 Each catalyst was fabricated in quantities of 5g on the same base of commercial Gibbsite (Al(OH)3 - Hydrargillite EMPLURA from Sigma-Alfrich) and hexachloroplatinic acid (H2PtCl6). For the preparation of the catalyst (Pt / Al2O3 exGibbsite-550) -550°C called “control”, i.e. not in accordance with the invention, calcination at 550°C of the Gibbsite (Al(OH)3) was first carried out to obtain the transition alumina (Al2O3) intended to serve as an impregnation support.This impregnation support is designated Al2O3 exGibbsite -550. This calcination of Gibbsite (Al(OH)3) before impregnation in the context of the production of the control catalyst was carried out in hot air, at 550°C, remaining for 2 hours at maximum temperature in a muffle furnace having a heating rate of 5°C / min, in the same way as in Example 1. The impregnation step was carried out in a manner analogous to Example 1, as follows: - 5 g of transition alumina Al2O3exGibsite taken after calcination of Gibsite (Al(OH)3 were impregnated by nascent humidity with 3.40 g of aqueous solution of hexachloroplatinic acid containing 0.025 g of platinum, in order to produce 5 g of catalyst (Pt / Al2O3exGibsite)-550°; and - 6.56 g of Gibsite (Al(OH)3) were used as a support impregnation of 3.97g of aqueous solution of hexachloroplatinic acid containing 0.025g of platinum, as part of the manufacture of the catalyst (Pt / Gibbsite)-550°C.The supports now impregnated with the aqueous solution of hexachloroplatinic acid were then dried and calcined at 550°C following the protocol described in Example 1. Validation of the composition and catalytic tests – Example 9 With reference to Table 7 below, the percentage of platinum deposited on the different supports was verified by ICP. As observed, the effective quantity of platinum deposited by incipient wetness impregnation varies between 0.46 and 0.55% by weight, which is very close to the theoretical target content. On this basis, the reproducibility of the incipient wetness impregnation method is also validated in the context of the use of Gibbsite.It follows that the behavior of the (Pt / Gibbsite) -550°C catalyst manufactured according to the manufacturing process can be validly compared with that of the (Pt / Al2O3 exGibbsite-550) -550°C catalyst manufactured in the usual way, on the basis of the same common denominator {Gibbsite - Pt content - calcination temperature}. [Table 7] Pt content Pt content Catalyst theoretical (%wt) actual (%wt). -550°C 0.5 0.46(Pt / Al2O3 exGibbsite-550) -550°C 0.5 0.55Results analysis – example 9 The reaction performances in catalytic combustion of dihydrogen were evaluated under the same stable operating conditions of example 1 and reported in figure 11. Figure 11 shows that the (Pt / Gibbsite) -550°C catalyst manufactured in accordance with the process according to the invention is active from room temperature with an average conversion of 23%. Also, the conversion into dihydrogen increases progressively with the increase in the furnace temperature, of the order of 50% conversion at the temperature of 53°C and more than 70% at 85°C. In comparison, the control catalyst (Pt / Al2O3 exBayerite-550) -550°C, whose manufacture differs only from that of the catalyst (Pt / Gibbsite) - 550°C in that the support was calcined before platinum impregnation, is inactive at room temperature and remains so up to 75°C.At 95°C, the conversion of dihydrogen by the catalyst (Pt / Al2O3 exBayerite-550) -550°C remains below 20%. On the basis of this example 9, it appears that the process according to the invention is also suitable for manufacturing Pt-alumina catalysts which meet the targeted performance criteria from Gibbsite. Thus, the process according to the invention does not appear to be limited to the use of a particular form of aluminum hydroxide. Even if in example 9 the catalysts manufactured from Gibbsite underwent calcination only at 550°C, the observation results reasonably lead us to admit that the performance results of Bayerite are generally transposable to those of Gibbsite and, more generally, to any form of aluminum hydroxide (Al(OH)3).Example 10 Test matrix – example 10 This example aims to verify whether the scope of the process extends to another type of alumina hydrate, a precursor of alumina, different from aluminum hydroxide (Al(OH). 3which is an alumina trihydrate. In this respect, this example 10 is based on a comparative analysis of catalytic activity between two Pt-alumina catalysts as listed in Table 5, which are manufactured from alumina monohydrate, Boehmite which is an aluminum oxo-hydroxide AlO(OH), including: - a Pt-Alumina catalyst referenced (Pt / Boehmite)-550°C, with a platinum content by weight of the order of 0.5%, obtained by directly impregnating the platinum salt on a Boehmite AlO(OH) support, followed by calcination at 550°C transforming the Boehmite AlO(OH) into alumina (Al2O3); and - a Pt-Alumina catalyst referenced (Pt / Al2O3exBoehmite)-550°C, with a platinum content by weight of the order of 0.5%, which is manufactured in the manner recommended in the state of the art, namely by impregnating the platinum salt on the alumina (Al2O3) obtained after the calcination of the Boehmite AlO(OH) at 550°C.[Table 8] SUPPORT ACTIVE PHASE CATALYST NOMENCLATURE Nature / Nature ContentPost-treatment (Pt / (support))-T°C Temperature (% wt) calcination impregnation Boehmite (Pt / Boehmite )- AlO(OH) 550°C 2 3 Calcination at Al O (ex- Pt 0.5 550 °C Boehmite (Pt / Al2O3 exBoehmite- calcined at 550) -550°C 550°C) Manufacturing – example 10 Each catalyst was manufactured in a quantity of 5g on the same base of commercial Boehmite (AlOOH-PURAL SB1, SASOL Chemicals) and hexachloroplatinic acid (H2PtCl6). For the preparation of the catalyst (Pt / Al2O3 exBoehmite-550) -550°C, a calcination at 550°C of Boehmite (AlO(OH)) was first carried out to obtain the transition alumina (Al2O3) intended to serve as an impregnation support. This impregnation support is designated Al2O3 exBoehmite-550.This calcination of Boehmite (AlO(OH)) before impregnation in the context of the production of the catalyst was carried out in hot air, at 550°C, remaining 2 hours at maximum temperature in a muffle furnace having a heating rate of 5°C / min, in the same way as in example 1. The impregnation step was carried out in a manner similar to example 1, using: - an impregnation with nascent humidity of 5.83 g of aqueous solution of hexachloroplatinic acid containing 0.025 g of platinum on 5 g of transition alumina Al2O3 exBoehmite-550, obtained by calcination at 550°C, in order to produce 5 g of catalyst (Pt / Al2O3 exBoehmite-550)-550°; and - an impregnation with nascent humidity of 5.80g of aqueous solution of hexachloroplatinic acid containing 0.025g of platinum on 5.89g of Boehmite (AlO(OH)) as part of the manufacture of the catalyst (Pt / Boehmite)-550°C.The supports now impregnated with the aqueous solution of hexachloroplatinic acid were then dried and calcined at 550°C following the same protocol as in Example 1. Validation of the composition – Example 10 With reference to Table 9, the percentage of platinum deposited on the different supports was verified by ICP. As observed, the effective amount of platinum deposited by humidity impregnation is 0.51 and 0.57% by weight, which is very close to the theoretical target content. On this basis, the reproducibility of the incipient humidity impregnation method is also validated in the context of the use of Boehmite. It follows that the behavior of the catalyst (Pt / Boehmite) - 550°C can be validly compared to that of the catalyst (Pt / Al2O3 exBoehmite-550)-550°C on the basis of the same common denominator {Boehmite - Pt content - calcination temperature}. [Table 9] Pt content Pt content Catalyst theoretical (%wt) actual (%wt). -550°C 0.5 0.51(Pt / Al2O3 exBoehmite-550) -550°C 0.5 0.57Catalytic tests and analysis of results – example 10 The reaction performances in catalytic combustion of dihydrogen were thus evaluated under the same stable operating conditions of example 1 and reported in figure 10. Figure 12 shows that the catalyst (Pt / Boehmite) -550°C and the catalyst (Pt / Al2O3 exBoehmite-550) -550°C both have no activity in catalytic combustion of dihydrogen from room temperature up to 80°C. At 95°C, the observed dihydrogen conversion remains below 10%. Example 10 thus made it possible to exclude Boehmite, which is an aluminium oxo-hydroxide (otherwise known as alumina monohydrate), from the alumina hydrates which are precursors of alumina for which the process according to the invention provides real added value in terms of the catalytic activity of the catalysts which it can be used to manufacture.Characterization In order to explain such a gain in catalytic activity of the catalysts resulting from a dispersion of platinum precursor on aluminum hydroxide before calcination to form alumina in accordance with the invention, compared to the catalysts whose platinum impregnation is carried out either on aluminum oxo-hydroxide (namely on alumina monohydrate) or in a known manner on alumina, a preliminary characterization study was carried out. This characterization study focused on the six catalysts, listed in Tables 2, 4 and 6, manufactured from Bayerite, Gibbsite and Boehmite with an iso-content of 0.5% by weight of platinum and at a support calcination temperature of 550°C. Referring to Figure 13, it is visually observable in Photo 1) that initially, Gibbsite, Bayerite and Boehmite have the same pale yellow tint.Following the impregnation of platinum directly onto Gibbsite, Bayerite and Boehmite followed by a freeze-drying step and calcination at 550°C, photo 2) reveals that: - the catalysts (Pt / Gibbsite) -550°C and (Pt / Bayerite) -550°C, each derived from an aluminium hydroxide in accordance with the process according to the invention, have a light grey tint; while - the catalyst (Pt / Boehmite) -550°C, non-compliant in that it is derived from an aluminium oxo-hydroxide, conversely retains the same pale yellow tint. Photos 3) and 4) show that the aluminas formed by calcination of Gibbsite, Bayerite and Boehmite, as well as the catalysts obtained following the impregnation of these aluminas with platinum followed by calcination at 550°C, all have roughly the same white color.This preliminary study suggests a correlation between the light grey colour of the (Pt / Bayerite) -550°C and (Pt / Gibbsite) -550°C catalysts, produced from aluminium hydroxide in accordance with the process according to the invention, and their substantial gain in catalytic activity observed compared to: - the corresponding "control" catalysts, (Pt / Al2O3 exBayerite -550) -550°C and (Pt / Al2O3 exGibbsite -550) -550°C respectively; as well as - the catalysts formed from Boehmite which is not an aluminium hydroxide (Al(OH). 3 ). This feature suggests a strong interaction between the PtCl6 anions 2-of hexachloroplatinic acid and the surface of the aluminum hydroxides impregnated with the hexachloroplatinic acid solution, leading to increased dispersions and inclusions of platinum in the aluminas formed after calcination. Process according to the invention and applications Based on the various examples 1 to 10, it was surprisingly observed by the test that the dispersion of platinum precursor on an aluminum hydroxide support, followed by post-drying calcination of the assembly {support + platinum precursor impregnated in the support} makes it possible to obtain more efficient Pt-alumina catalysts with iso- platinum content than in the case of a dispersion of platinum precursor on alumina followed by drying and calcination.In particular, calcination of the aluminum hydroxide supports, in which the platinum precursor is dispersed, in the temperature range [250°C-1000°C] with catalysts: - active in the combustion of dihydrogen from room temperature; and - ensuring substantially complete combustion at 100°C. Calcination at a temperature in the range [350°C-850°C], and more specifically in the reduced range [550°C-650°C] makes it possible to obtain the most efficient Pt-alumina catalysts. It is therefore recommended to equip the burner with a catalytic combustion lamp of dihydrogen with a Pt-alumina type catalyst manufactured on this basis, to achieve active and efficient combustion of dihydrogen from room temperature. This arrangement thus makes it possible to avoid an accumulation of dihydrogen after passing over the burner, which otherwise could lead to a risk of explosion.It should be noted that the invention is not limited solely to the chosen way of manufacturing a Pt-alumina type catalyst which is particularly suitable for the catalytic combustion of dihydrogen from room temperature. It is understood that the use case of combustion of dihydrogen by means of a Pt-alumina catalyst which was manufactured in accordance with the implementation described does not obviously depart from the scope of the invention. The performance tests carried out on all the batches (Pt / bayerite)-T°C and (Pt / gibbsite)-T°C during this study are all transcribed examples of implementation of combustion of dihydrogen by means of a Pt-alumina catalyst manufactured in accordance with the method according to the invention. Indeed, the catalytic activity of the catalysts was assessed under conditions of combustion of dihydrogen, advantageously initiated from room temperature.It will be advantageously preferred to integrate into a catalytic lamp a catalyst manufactured in accordance with the method according to the invention for a calcination temperature belonging to the range [550°C -650°C], retained as the most efficient. It should be noted, however, that the manufacturing method according to the invention is not limited to providing catalysts for such an application of catalytic lamp, or other domestic device with catalytic combustion for the diffusion of perfume and / or active substances, for the destruction of odorous or non-odorous molecules, and / or for air purification. Given that such Pt-alumina type catalysts ensure a greater heat release due to the fact that the dihydrogen is better consumed, they can thus find an application, for example, in domestic or commercial heating, gas turbines, the nuclear industry or even in fuel cells.

Claims

CLAIMS 1. Catalyzed process for the combustion of dihydrogen comprising: - the provision of at least one catalyst comprising a catalytically active phase of platinum (Pt) and an alumina (Al2O3) support, and - the supply of dihydrogen (H2) forming fuel in the vicinity of said at least one catalyst to be burned therein; in which the catalyst provided is obtained at the end of the successive steps of: - S1) provision of an aluminum hydroxide (Al(OH)3) support; - S2) dispersion in said support of a platinum precursor, the decomposition of which by calcination forms the catalytically active phase; - S3) treatment of the support in which the platinum precursor is dispersed at the end of step S2), comprising a sub-step S31) of drying followed by a sub-step S32) of calcination at a target temperature between 250°C and 1000°C to jointly: -- transform the aluminum hydroxide (Al(OH)3) of the support into alumina (Al2O3);and -- obtaining the catalytically active phase from the precursor dispersed in the support in step S2).

2. Catalyzed process for the combustion of dihydrogen according to claim 1, characterized in that the dihydrogen forming fuel is burned at room temperature.

3. Catalyzed process for the combustion of dihydrogen according to claim 1 or 2, in which the catalyst used has a platinum (Pt) content of between 0.3 and 1% by weight.

4. Catalyzed process for the combustion of dihydrogen according to claim 2 or 3, characterized in that the catalyst used is integrated in a device for the diffusion of perfume and / or active substances; for the destruction of odorous or non-odorous molecules, and / or for air purification.

5. Catalyzed process for the combustion of dihydrogen according to any one of claims 1 to 4, in which the aluminum hydroxide provided to form alumina (Al2O3), at the end of the treatment step S3), of the support of said at least one catalyst used is Bayerite (Al(OH)3).

6. Catalyzed process for the catalytic combustion of dihydrogen according to claim 5, in which the calcination temperature in sub-step S32) is between 550°C and 650°C.

7. Catalyzed process for the combustion of dihydrogen according to any one of claims 1 to 4, in which the aluminum hydroxide provided to form alumina (Al2O3), at the end of the treatment step S3), of the support of said at least one catalyst used is Gibbsite (Al(OH)3). 8.Catalyzed process for the catalytic combustion of dihydrogen according to claim 7, wherein the calcination temperature in sub-step S32) is set at substantially 550°C.

9. Catalyzed process for the combustion of dihydrogen according to any one of the preceding claims, wherein: - sub-step S31) of drying the impregnated support includes freezing at a temperature of -18°C for 12 hours followed by freeze-drying for 12 hours; and - sub-step S32) of calcination is ensured by a gradual increase in temperature until reaching the target temperature, followed by maintenance at the target temperature for two hours, during the treatment step S3) at the origin of obtaining said at least one catalyst used.

10. Catalyzed process for the combustion of dihydrogen according to any one of the preceding claims, wherein, at the origin of obtaining said at least one catalyst used, step S2) of dispersing the precursor in the support provided in step S1) is carried out by impregnation or by exchange.

11. Catalyzed process for the combustion of dihydrogen according to any one of the preceding claims, wherein the platinum precursor used in step S2), at the origin of obtaining said at least one catalyst used, is a solution of hexachloroplatinic acid (H 2 PtCl 6 ) or a solution of tetraammineplatinum dichloride (Pt(NH3)4Cl2).

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