IT202100017624A1 - Process for the production of a tablet for the generation of gaseous hydrogen from water and its control - Google Patents

Description

DESCRIPTION

Attached to a patent application for INDUSTRIAL INVENTION having the title

?Process for the production of a tablet for the generation of gaseous hydrogen from water and its control?

FIELD OF THE INVENTION

The present invention relates to a process for the production of a tablet comprising a mechanically activated and pressed powder, or, alternatively, incorporated within a water-soluble polymer. The object of the present invention is also said tablet or a device comprising it and their use for the production of gaseous hydrogen from water in a controlled manner.

STATE OF ART

Thanks to the wide possibilities of use (from combustion to the generation of electricity), hydrogen? considered worldwide one of the most interesting energy vehicles useful, among other purposes, to assist the process of decarbonisation of the planet. However, despite being the most? element? abundant in nature, hydrogen? present in the free state but only linked to other elements. Also, hydrogen gas (H2) ? difficult to store safely. A solution to this problem? that of producing hydrogen starting from other substances such as water or hydrocarbons. In this case, hydrogen is generally categorized according to the mode of production. ? It is therefore possible to distinguish between:

- Black hydrogen: produced from water through electrolysers fed with current from coal-fired plants;

- Gray hydrogen: produced from hydrocarbons with release of CO2 into the environment;

- Blue hydrogen: produced from hydrocarbons without release of CO2 into the environment;

- Purple hydrogen: produced by water through electrolysers powered by current from nuclear power plants;

- Green hydrogen: produced from water through electrolysers fed with current from renewable sources; and finally - White hydrogen: produced from water through suitable metal powders without the use of electricity.

It therefore appears clear that the so-called ?white hydrogen?, compared to other types of hydrogen, is extremely interesting since, although it is obtained from water, the process for its production does not require electricity. On the contrary, during its generation, heat is produced which can be used for various purposes. In other words, is it the only type of hydrogen that? associated with an energy release instead of? to a consumption.

In the current state of the art, white hydrogen ? produced thanks to the use of both composite and non-composite metal powders, which capture the oxygen of the water releasing the hydrogen.

Processes for obtaining such powders are known and are described for example in EP3713674 which reports a method for the mechanical processing and activation of metallic and non-metallic powders. However, one of the main problems of such a technology? linked to the fact that, through the use of the powders directly obtained with this method, there is too rapid and often uncontrolled generation of hydrogen gas. This turns out to be a disadvantage as many applications require a constant and controlled release instead.

The present invention solves the above problems by making available a process for making a tablet which, thanks to the specific composition of the powder mixture used for its production and/or to the specific degree of compression with which said tablet ? made and/or to the incorporation of said powders within a water-soluble polymeric matrix and/or to the inhibition of one or more? faces with a waterproof coating and/or with a layer of a powder or a mixture of inert powders, it allows to slow down and/or regulate the contact between water and powders making s? that the production of gaseous hydrogen from water takes place in a controlled way.

SUMMARY OF THE INVENTION

The present invention relates to a process for the production of a tablet comprising a powder activated mechanically and pressed, or, alternatively, incorporated within a water-soluble polymer, said powder being obtained starting from a mixture of powders comprising:

(a) between 70% and 99% by mass of an aluminum powder;

(b) between 0.5 and 20% by mass of a bismuth powder;

(c) between 0.5 and 20% by mass of a powder selected from the group consisting of: a salt powder, a water-soluble polymer powder, a sugar powder, or a combination thereof.

The object of the present invention is also a tablet obtainable by means of said process. The invention also relates to a tablet comprising at least two layers having a different degree of compression obtained with the process of the invention but subjecting each layer to a different compression force. Alternatively, said tablet can? comprising at least two layers having a different mechanically activated powder composition, in particular containing a mechanically activated powder obtained starting from a mixture of powders comprising a different powder (c) in each layer. Optionally, said at least two layers having a different composition can also have a different degree of compression as described above.

Each tablet according to the present invention can furthermore be coupled with another tablet obtained with the process according to the present invention but in which the mixture of powders (a)-(c) is? replaced with a mixture of inert powders, meaning that they do not react with water to produce hydrogen.

According to one embodiment, each tablet according to the present invention can include at least a waterproof coating on one or more? faces and/or have a shape characterized by a height/diameter ratio between 0.1 and 20.

The present invention also relates to a device comprising at least one tablet as described above.

The present invention also relates also to a mechanically activated powder obtained starting from a mixture of powders (a)-(c) as described above, the process for obtaining it and its use for the production of gaseous hydrogen from water.

A further object of the present invention is the use of said tablet or of said device for the production of gaseous hydrogen from water in a controlled manner.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 shows the evolution of hydrogen over time from tablets obtained with different degrees of compression and having the same composition in terms of mechanically activated powder, the same shape and the same height/diameter ratio of 0.62 compared to the powder mechanically activated in free form as described in Example 1. Figure 2 shows the correlation between the compression force used to produce the tablet according to the present invention and the increase in the time required to reach 90% of the maximum hydrogen evolution for kg of mechanically activated powder compared to mechanically activated powder in free form as described in Example 1.

Figure 3 shows an embodiment of the present invention in which the pads have a three-sided (?C1?), two-sided (?C2) or single-sided (?C3?) water impermeable coating as described in the ?Example 2.

Figure 4 shows the evolution of hydrogen over time from pellets having the same composition in terms of mechanically activated powder and subjected to the same compressive force of 1.16 kN but with different height/diameter ratios and/or face inhibition in comparison to the mechanically activated powder in free form as described in Example 2.

Figure 5 shows some of the various possible embodiments of the pellets of the present invention: pellet comprising two layers having different composition Al/Bi/water soluble polymer Al/Bi/salt (?a?), pellet comprising two layers having different composition Al /Bi/water soluble polymer Al/Bi/salts a tablet/layer of inert powders coupled to the Al/Bi/water soluble polymer layer, and coated on the other three faces with an impermeable coating (?b?), tablet comprising two layers having different composition Al/Bi/water soluble polymer Al/Bi/salt and coated on three faces with an impermeable coating (?c?), tablet comprising three layers having different composition Al/Bi/salt Al/Bi/water soluble polymer Al/Bi/salt and coated on both sides with a waterproof coating (?d?)

Figure 6 shows possible alternative forms of the tablet of the present invention in the case of the embodiment in which the tablet is obtained by a process comprising step (iv.b). These possible shapes include a solid cylindrical shape without holes (?a?), with a central cylindrical through hole (?b?), with a central cylindrical non-through hole (?c?), with a central star through hole (? d?). Said possible shapes are also applicable to the other embodiments of the tablet according to the present invention.

Figure 7 shows the granulometric curves of mechanically activated powders obtained starting from mixtures of powders according to the present invention comprising, as powder (c): 1) MgCl2; 2) CaCl2; 3) NaCl; 4) NH4Cl.

Figure 8 shows the granulometric curve highlighting the different dimensional distribution of a mechanically activated powder obtained starting from a mixture of powders according to the present invention but comprising, instead of powder (c), a zinc powder.

Figure 9 shows the evolution of hydrogen over time of mechanically activated powders obtained starting from mixtures of powders according to the present invention comprising, as powder (c): MgCl2; CaCl2; NaCl; and NH4Cl, in comparison with a mechanically activated powder obtained starting from a mixture of powders according to the present invention but comprising, instead of powder (c), a zinc powder as described in Example 3.

DETAILED DESCRIPTION OF THE INVENTION

For the purposes of the present invention with the term ?white hydrogen? refers to the gaseous hydrogen (H2) produced from water through the use of a metal powder or a mixture of powders including metal powders without the use of electricity.

For purposes of the present invention, for ?aluminum powder? does it mean a metallic aluminum powder, or an aluminum powder in its oxidation state ?0? (Al<0>).

For purposes of the present invention, for ?bismuth powder? is meant a metallic bismuth powder, i.e. a bismuth powder in its oxidation state ?0? (Bi<0>).

For purposes of the present invention, for ?acoustic resonant mixer? it means a machine that promotes the mixing of one or more? substances charged inside it by means of oscillations with a frequency close to the resonance frequency of the internal system.

For purposes of the present invention for ?mechanically activated powders? it is understood that said powders, with respect to the starting powders, turn out to have a variation of the size (granulometry), of the morphology, of the structure and/or of the composition of the initial material. In other words, this activation means that said powders undergo a modification of their specific surface, shape and/or composition, thus resulting in a reactivity? also modified. The final product? identifiable as a single powder which is defined as ?mechanically activated?.

The present invention relates to a process for making a tablet for generating gaseous hydrogen from water, or in other words, for generating ?white hydrogen? gaseous from water.

The process according to the present invention comprises the steps of:

(i) make available a blend of powders comprising:

(a) between 70% and 99% by mass of an aluminum powder;

(b) between 0.5 and 20% by mass of a bismuth powder;

(c) between 0.5 and 20% by mass of a powder selected from the group consisting of: a salt powder, a water soluble polymer powder, a sugar powder, or a combination thereof;

(ii) loading said mixture of powders into a mixer comprising spheres;

(iii) operating said mixer at an acceleration ranging from 50 G to 100 G, preferably for a time ranging from 5 to 300 minutes, until a mechanically activated powder is obtained;

(iv.a) pressing said mechanically activated powder obtained in step (iii) into a tablet mold by a compressive force of between 0.5 and 150 kN;

or, alternatively,

(iv.b) inserting said mechanically activated powder obtained in step (iii) into a water-soluble polymer in the molten state and subsequently casting it into a tablet mold or extruding it.

Preferably, step (iii) of operating said mixer is spaced out by a number of pauses between 1 and 200, preferably between 1 and 100, more? preferably between 5 and 20, said pauses preferably having a time duration between 0.5 and 20 minutes each, preferably between 1.0 and 5 minutes each. By "pause", for the purposes of the present invention, we mean not only the stop of the mixer but also, optionally, a reduction of the acceleration below the value of 50 G.

According to an embodiment of the invention, said aluminum powder (a) and/or said bismuth powder (b) has/have an initial particle size ? 4000 ?m, preferably ? 1000 ?m, pi? preferably ? 200 ?m, even more? preferably ? 100 ?m.

Preferably, said aluminum powder (a) ? in a quantity between? 80 and 99% by mass, more? preferably between 90 and 97% by mass. Preferably, said bismuth (b) powder? in a quantity between l?1 and 10% by mass, more? preferably between 3 and 5% by mass.

According to one embodiment, said powder (c) ? a mixture of a salt powder and a water soluble polymer powder, or a salt powder and a sugar powder, or a water soluble polymer powder and a sugar powder.

Preferably, said salt ? selected from the group consisting of: NaCl, KCl, LiCl, CaCl2, YCl3, AgCl2, MgCl2, NH4Cl, and a combination thereof.

Preferably, said water-soluble polymer ? selected from the group consisting of: polyethyl-2-oxazoline with molecular weight ?500000, preferably ?50000, PEG/PEO with molecular weight ? 1000000, and a combination thereof.

Preferably, said sugar ? selected from the group consisting of: a monosaccharide sugar, preferably glucose, a polysaccharide sugar, preferably sucrose, and a combination thereof.

According to a preferred embodiment of the invention, said mixer of step (ii) is an acoustic resonant mixer, preferably a two, three or more acoustic resonant mixer masses. Preferably, said acoustic resonant mixer ? an acoustic resonant mixer with vertical, horizontal or combined action.

Preferably said mixer, pi? preferably said acoustic resonant mixer comprises a mixing jar (also called activation jar) comprising said spheres and into which said mixture of powders made available in step (i) is inserted. Pi? preferably, said mixing jar ? characterized by having an internal volume between 0.010 liters and 500 liters, even more? preferably between 0.05 liters and 50 litres.

According to one embodiment, the apparent volume of said spheres with respect to the volume of said jar, in other words, the apparent volumetric filling of the jar, is between 12.5 and l?87.5%, preferably between 25 and 75%, even more? preferably between 45 and 60%.

According to one embodiment, said jar has a shape chosen from: cylindrical, prismatic or prismatic with rounded corners.

Preferably, said jar ? a jar of a material selected from the group consisting of: steel, titanium, tungsten carbide, silicon carbide, zirconium oxide, plastic materials, Teflon, and a combination thereof.

According to one embodiment, the spheres used in the process according to the present invention are spheres of a material selected from the group consisting of: steel, titanium, tungsten carbide, silicon carbide, zirconium oxide, plastic materials, Teflon, and one thereof combination. Said spheres preferably have a diameter between 1 mm and 50 mm, more preferably between 1 mm and 20 mm.

According to one embodiment, the mixer comprises two different types of spheres, i.e. spheres having two different diameter values and in which the ratio between the diameter pi? large of a type of spheres and the diameter pi? small of the other type of spheres ? between 1.1 and 50, preferably between 1.25 and 5.

According to another embodiment, the mixer comprises three different types of spheres, ie spheres having three different diameter values.

According to an embodiment, the ratio between the weight of said spheres and the weight of the mixture of powders loaded in step (ii) of the process according to the present invention ? between 1:1 and 100:1, preferably between 20:1 and 5:1.

According to one embodiment, said spheres are replaced with spheroidal elements, rollers, needle rollers or a combination thereof, preferably having a volume equal to that of the spheres they replace. Preferably, the apparent volume of said spheres relative to the volume of said mixer, in other words, the apparent volumetric filling of the mixer, is between 12.5 and l?87.5%, preferably between 25 and 75%, even more? preferably between 45 and 60%.

According to one embodiment, the process according to the present invention comprises, after step (ii) and before step (iii) a step:

(ii.a) to add a process control agent to said mixer. Preferably said process controller agent ? selected from the group consisting of: acetone, pentane, cyclopentane, hexane, cyclohexane, PEG, PPG, and a combination thereof.

Said passage? preferably as described in EP3713674, incorporated herein entirely.

Preferably, in said step (ii.a) of the process according to the present invention, the ratio between the volume of said process control agent and the mass of the powder mixture fed to step (ii) ? between 0.1 ml/g and 50 ml/g.

According to one embodiment, said process controller agent ? added in said mixer up to a volumetric filling equal to 100% of its volume.

Preferably, said mixer ? an acoustic resonant mixer as described above. According to one embodiment, said mixer, preferably said acoustic resonant mixer, comprises a mixing jar as described above. In this case we therefore speak of volumetric filling equal to 100% of the volume of said jar.

Without wanting to bind to a specific theory, ? Is it possible to argue that the addition of said process controller agent allows you to regulate further and more? finely the characteristics of the mechanically activated powder obtained after step (iii), such as for example its granulometry and/or purity since, acting as a dispersing material inside the mixer, it favors the mechanical activation of the initial powder mixture arrangement at step (i) and allows for better temperature control during mixing step (iii). Consequently, also the final characteristics of the pad, obtained with step (iv.a) or (iv.b) will be improved. According to an embodiment which does not include said step (ii.a), or in the case of a volumetric filling < 100%, the process according to the present invention comprises a step:

(ii.b) to fill the optionally free volume of said mixer with an inert gas, preferably selected from the group consisting of: dry air, argon, nitrogen, helium, and a combination thereof.

Said passage? preferably as described in EP3713674, incorporated herein entirely.

Preferably, said mixer ? an acoustic resonant mixer as described above. According to one embodiment said mixer, preferably said acoustic resonant mixer comprises a mixing jar as described above. In this case we therefore speak of filling the volume of said jar.

Without wanting to bind to a specific theory, ? possible to argue that such a passage of filling with an inert gas allows to reduce the probability? of ignition of the powder mixture charged in step (ii) or other side processes which may occur in the case of the presence of oxygen and which may reduce the purity of the mechanically activated powder obtained in step (iii).

According to an embodiment, in step (iii) of the process according to the present invention, said mixer ? activated to an acceleration preferably between 70 G and 90 G, more? preferably between 75 and 85 G.

Preferably, said mixer ? active for a time between 5 and 60 minutes, plus? preferably between 10 and 20 minutes.

The powder obtained after step (iii) of the process according to the present invention ? defined as a mechanically activated powder. Preferably, said mechanically activated powder ? a composite aluminum/bismuth powder and a salt, water soluble polymer, sugar or combination thereof depending on the powder chosen (c) in step (i) described above.

In other words, the process according to the present invention allows to obtain, downstream of step (iii), a powder in which the particles making up the powder are aluminium/bismuth composite particles and a salt, a water-soluble polymer, a sugar or a their combination according to the powder selected (c) in step (i) described above.

Preferably, said mechanically activated powder obtained in step (iii)? characterized by having an average diameter, measured by particle size analysis, lower than 1000 µm, preferably between 50 and 400 µm.

Pi? preferably, said mechanically activated powder obtained in step (iii)? characterized by having a homogeneous distribution of the values of said diameter around the mean value.

Without wanting to be bound to a specific theory, the Applicant has found that the specific formulation of the mixture of powders and in particular the choice of powder (c), i.e. a powder selected from a powder of a salt, a water-soluble polymer, a sugar or a combination of them, is an essential element for scalability? of the process according to the present invention. Indeed, said powder (c) acts as an agent which helps the grinding and mixing of the mixture of powders inside the mixer effectively preventing the formation of too large particles and/or agglomerates of powder, effectively acting as an anti-adhesion agent as well as ? as a coating agent for metal powder particles. In addition to what already? said, ? important to note that the possibility? of dissolving in water, linked to the water-soluble nature of said salt, of said water-soluble polymer and/or of said sugar, increases the level of porosity? of the mechanically activated powder particles that form the tablet. This implies that, during the reaction with water, you can have a pi? rapid and efficient generation of hydrogen. At the same time, the specific degree of compression of the mechanically activated powder (step (iv.a)) or the insertion of said mechanically activated powder inside a water-soluble polymer in the molten state (step (iv.b)) allows a control effective speed? of contact/penetration of water resulting in a tablet that allows a controlled production of hydrogen.

According to the embodiment in which the process according to the present invention comprises step (iv.b), the mechanically activated powder inserted into the water-soluble polymer in the melt state which is subsequently poured into a tablet mold or extruded, is in a quantity between 10 and 95% by mass, preferably between 50 and 90% by mass, even more? preferably between 75 and 90% by mass.

Said water soluble polymer ? preferably selected from the group consisting of: PEG, PEO, polyvinylpyrrolidone, PVA, PEOX, and a combination thereof. In one embodiment, said water soluble polymer ? brought to the melting point, preferably in an inert atmosphere. The mechanically activated powder obtained in step (iii) is then added, thus obtaining? a paste, which is poured into a tablet mold and left to cool. In one embodiment, said water soluble polymer ? preferably dissolved before adding the mechanically activated powder in an organic solvent selected from the group consisting of: a ketone, preferably acetone, toluene, ethyl acetate, petane, cyclopentane and a combination thereof. According to this embodiment, once the paste obtained has been poured into a mold for tablets, said mold is placed in the oven to allow the slow evaporation of the solvent.

According to another embodiment, said water-soluble polymer loaded with said mechanically activated powder? extruded to form a tablet in the desired geometry.

The present invention also relates to a tablet obtainable/obtained with the process described above comprising step (iv.a). Advantageously, thanks to the specific composition of the mixture of powders, their mechanical activation to form a mechanically activated powder and the degree of compression obtained with the aforementioned steps (i)-(iv.a), said pellet allows to generate gaseous hydrogen, once in contact with water, in a controlled way.

The present invention also relates to a tablet obtainable/obtained with the process described above comprising step (iv.b).

The present invention also relates to a process for making a tablet for generating gaseous hydrogen from water in which said tablet comprises at least two layers having two different degrees of compression.

Said process therefore comprises a step (v) of coupling, by compression and/or an adhesive:

- At least a first layer obtained by subjecting the mechanically activated powder of step (iii) described above to a step (iv.a?) of pressing said mechanically activated powder in a tablet mold by means of a compressive force between 0.5 and 150 kN, preferably between 0.5 and 10 kN;

- With at least a second layer obtained by subjecting the mechanically activated powder of step (iii) described above to a step (iv.a??) of pressing said mechanically activated powder in a tablet mold by means of a compressive force between 80 and 150 kN, preferably between 0.5 and 10 kN.

The object of the present invention is also a tablet obtainable with said process (steps (i)-(v) described above). Advantageously, said pad, thanks to the coupling of the aforesaid at least two layers having different degrees of compression, allows to calibrate and control in a desired way the speed? of production of gaseous hydrogen from water. Without wanting to be bound by a specific theory, the Applicant has nevertheless found that by varying the degree of compression of the mechanically activated powder (in fact producing tablets having different degrees of compression or comprising at least two layers having different degrees of compression), ? is it possible to vary the speed? of hydrogen production. As also demonstrated in the examples section, pi? the degree of compression? high (ie the more the applied compressive force is high), the more? the times of generation of hydrogen lengthen (that is, the slower and more controlled the production of hydrogen will be), as the contact between the water and the particles of the reactive powders will take place? more slowly.

The present invention also relates to a process for manufacturing a tablet for generating gaseous hydrogen from water in which said tablet comprises at least two layers having different compositions in terms of composition of the mechanically activated powder.

Said process therefore comprises a step (v?) of coupling, by compression and/or an adhesive, at least two layers obtained according to steps (i)-(iv.a) of the process according to the present invention as described above and in which the composition of the powder (c) selected to produce said at least one first layer differs from the composition of the powder (c) selected to produce said at least one second layer as, for example, shown in Figure 5 ?a?.

In other words, according to an embodiment, said step (v?) comprises coupling by compression and/or an adhesive:

- at least a first layer, obtained according to steps (i)-(iv.a) of the process according to the present invention as described above and in which (c) ? a powder of a salt and/or sugar;

- with at least a second layer obtained according to steps (i)-(iv.a) of the process according to the present invention as described above and in which (c) ? a powder of a water-soluble polymer.

According to an alternative embodiment, said step (v?) comprises coupling by compression and/or an adhesive:

- at least a first layer obtained according to steps (i)-(iv.a) of the process according to the present invention as described above and in which (c) ? a powder of a salt;

- with at least a second layer obtained according to steps (i)-(iv.a) of the process according to the present invention as described above and in which (c) ? a powder of a water-soluble polymer and/or a sugar.

According to a further embodiment, said step (v?) comprises coupling by compression and/or an adhesive:

- at least a first layer obtained according to steps (i)-(iv.a) of the process according to the present invention as described above and in which (c) ? a powder of a sugar;

- with at least a second layer obtained according to steps (i)-(iv.a) of the process according to the present invention as described above and in which (c) ? a powder of a water soluble polymer and/or salt.

The present invention also relates to a tablet obtainable/obtained with said process (steps (i)-(v) described above).

Advantageously, thanks to the coupling of the aforesaid at least two layers having different composition in terms of mixture of powders used to produce the mechanically activated powder, said pellet allows to calibrate and control in a desired way the speed? of production of gaseous hydrogen from water.

Without wanting to be bound by a specific theory, the Applicant has nevertheless found that by varying the composition of said at least two layers inside a tablet (in fact producing tablets comprising at least two layers having a different composition), ? is it possible to vary the speed? of hydrogen production. By way of example, by coupling a layer comprising a mechanically activated powder obtained starting from a mixture of aluminium, bismuth and salt powders with a layer comprising a mechanically activated powder obtained starting from a mixture of aluminum, bismuth and a polymer water-soluble, depending on the respective nature of said salt and of said water-soluble polymer, a layer will allow? one more fast penetration of? water inside and therefore a pi? fast contact between the particles of the mechanically activated powder and the water (due to a more rapid dissolution of said particles) while the other layer will delay? said contact (due to a slower dissolution of the mechanically activated powder particles which are therefore ?protected? by water for a longer time).

According to an embodiment, the aforementioned at least one first layer which differs from the composition of the powder (c) chosen for the aforementioned at least one second layer, are obtained by subjecting the mechanically activated powder obtained to step (iii) of the process according to the present invention as described above:

- to a step (iv.a?) of pressing said mechanically activated powder into a tablet mold by a compressive force between 0.5 and 150 kN, preferably between 0.5 and 10 kN for said at least one first layer,

and to a step (iv.a??) of pressing said mechanically activated powder into a tablet mold by a compressive force of between 0.5 and 150 kN, preferably between 0.5 and 20 kN for said at least one second layer or vice versa.

The present invention also relates to a tablet obtainable/obtained with said process and comprising at least two layers having both different composition and degree of compression. Advantageously, said pad, thanks to the coupling of the aforementioned at least two layers having both different compression degrees and compositions, allows to further calibrate and control the speed in a desired way. of production of gaseous hydrogen from water further expanding the advantageous effects described above, separately, for each embodiment.

A further object of the present invention is a tablet obtained by coupling, by compression and/or an adhesive:

- At least one first tablet obtainable/obtained with the process according to the present invention comprising the step (iv.b) described above;

- With at least one second tablet obtainable/obtained with the process according to the present invention comprising the step (iv.a) described above.

According to one embodiment, said at least one second tablet ? a tablet comprising at least two layers having different degrees of compression obtainable with the process according to the present invention comprising step (v) as described above. According to one embodiment, said at least one second tablet ? a tablet comprising at least two layers having different compositions obtainable with the process according to the present invention comprising step (v2) as described above. According to one embodiment, said at least one second tablet ? a tablet obtainable/obtained with the process according to the present invention comprising step (v?) as described above ? characterized in that said at least two layers not only have different compositions but also different degrees of compression obtained by subjecting at least one layer to one pass (iv.a?) and at least another layer to one pass (iv.a??) as above described.

A further object of the present invention is a tablet according to any of the embodiments described above coupled with at least one further tablet obtained with the process according to the present invention but making available, as an alternative to step (i), a powder or a mixture of inert powders (i.a) selected from the group consisting of: aluminum oxides, iron oxides, aluminum hydroxides, or a combination thereof as shown for example in Figure 5 ?b?.

Advantageously, such a tablet, thanks to the coupling of the aforesaid at least two tablets (which in fact create at least two layers in which one layer is in fact an inert layer to the hydrogen production reaction), allows to delay in a controlled manner the contact between the? water the mechanically activated powder that ? on the other hand, it is active towards the reaction for the production of hydrogen. Such an embodiment can be seen as a? temporary inhibition of at least one side of the pad which allows for a controlled and ?on demand? release of hydrogen? unlike what happens instead in the case of a mechanically activated powder in free form in which there is an uncontrolled generation of hydrogen.

Preferably, the tablet of the present invention according to any of the embodiments described above can be produced in any desired geometric shape either by the process comprising step (iv,a) or by the process comprising step (ivb). Preferably called geometric shape ? choice between: cube, cylinder, sphere, rectangular parallelepiped, ovoid, ellipsoid.

According to one embodiment, the tablet of the present invention can have a shape that includes a central hole, through or blind, preferably a star-shaped or cylindrical hole, preferably as shown, for example, in Figure 6.

According to one embodiment, the tablet according to the present invention, according to any of the embodiments described above can have a shape characterized by a height/diameter ratio between 0.1 and 20, plus? preferably between 0.5 and 10. According to a particularly preferred embodiment, the tablet according to the present invention, according to any of the embodiments described above, can include, on at least one external surface, a waterproof coating such as, for example, shown in Figure 5 ?b?, ?c? or ?d?. Preferably said waterproof coating? chosen from the group consisting of: PLA, ABS, PET, PETG or other plastic-based polymers, a phenolic resin, an epoxy resin, a polyester resin, a vinylester resin, and a combination thereof.

In other words, such an embodiment provides the inhibition of one or more? external surfaces of the pad, cio? of one or more faces, making them effectively unavailable for reaction with water. Depending on the type and / or quantity? of inhibited faces/surfaces, the tablet of the present invention allows to be able to further calibrate the speed? of hydrogen production. Such a possibility? to have such a further control, in addition to the embodiments described above which also allow you to adjust the speed? of hydrogen produced, is particularly advantageous for the purposes of the present invention.

Without wanting to be bound to a specific theory, the Applicant has however found that the choice of the aforementioned height/diameter ratio value and/or of the inhibition of one or more? faces of the pad (by means of coupling with a layer made starting from a powder or a mixture of inert powders (i.a) and/or an impermeable layer as described above) allows to obtain the desired speed control? of hydrogen production, which turns out to be surprisingly better than using a mechanically activated powder in free form.

Without wanting to be bound by a specific theory, the Applicant has found that thanks to the shape of the tablet and/or to the specific height/diameter ratio, and/or to the compression force used for its production, and/or to the specific formulation of the mixture of powders (a)-(c) used to obtain mechanically activated powder, and/or in the presence of inhibition of one or more? faces, and/or the coupling with a layer formed by a powder or a mixture of inert powders, and/or the type of water-soluble polymer chosen in step (iv.b) and/or the quantity? of mechanically activated powder inserted inside said water-soluble polymer of step (iv.b), ? is it possible to effectively adjust the speed? whereby the water comes into contact with the mechanically activated dust particles thus controlling the generation of hydrogen.

The object of the present invention is a device for the production of gaseous hydrogen from water comprising a main body defining a containing volume comprising at least one tablet according to any of the embodiments described above.

Preferably, said device ? characterized in comprising at least one inlet opening for the water and, optionally, at least one outlet opening for the gaseous hydrogen produced by said at least one tablet once in contact with said water.

Preferably, said containment volume ? shaped in such a way that only an external surface of said tablet can come into contact with said water.

According to one embodiment, said device ? a cartridge.

The present invention also relates to a process for making a mechanically activated powder for the generation of gaseous hydrogen from water, or in other words, for the generation of ?white hydrogen? gaseous from water as described above.

Such a process comprises the steps (i)-(iii) of the process according to any of the embodiments as previously described. A further object of the present invention is a powder obtained/obtainable after step (iii) of the process according to the present invention and its use for the production of gaseous hydrogen from water. Said powder? defined as a mechanically activated powder. Preferably, said mechanically activated powder ? a composite aluminum/bismuth powder and a salt, water soluble polymer, sugar or combination thereof depending on the powder chosen (c) in step (i) described above.

In other words, the process according to the present invention allows to obtain, downstream of step (iii), a powder in which the particles making up the powder are aluminium/bismuth composite particles and a salt, a water-soluble polymer, a sugar or a their combination according to the powder selected (c) in step (i) described above.

Preferably, said mechanically activated powder obtained in step (iii)? characterized by having an average diameter, measured by particle size analysis, lower than 1000 µm, preferably between 50 and 400 µm.

Pi? preferably, said mechanically activated powder obtained in step (iii)? characterized by having a homogeneous distribution of the values of said diameter around the mean value.

Without wanting to be bound to a specific theory, the Applicant has however found that, thanks to the specific formulation of the initial powder mixture (a)-(c) and in particular the choice of powder (c), i.e. a powder selected from a a salt, a water-soluble polymer, a sugar or a combination thereof, ? It is possible to scale the process for obtaining said mechanically activated powder upwards, i.e. towards large production volumes. ? it was in fact possible to observe that, even using a jar having a high internal volume, preferably greater than 50 litres, more? preferably between 50 and 500 litres, ? Is it possible to obtain, after step (iii) of the process described above, a powder having not only the mechanical functionalization but also the granulometry and the capacity? to produce hydrogen you want, which is not ? equally true/possible if, instead of the particular powder (c) according to the present invention, another type of powder is used, such as, for example, zinc powder. Furthermore, as also demonstrated in the examples section, this specific formulation of the initial powder mixture (a)-(c) also influences the capacity? of hydrogen production by the mechanically activated powder itself, compared to an initial powder mixture comprising a different powder (c).

A further object of the present invention is the use of the tablet or device, preferably of the cartridge, according to any of the embodiments described above for the production of gaseous hydrogen starting from water. Advantageously, such a production of hydrogen ? a production that takes place in a controlled manner. How already? said, in fact, the tablet according to the present invention (and, therefore, also the device which comprises it) allows to limit and/or regulate the contact between water and the mechanically activated powder which forms it by making itself? that the production of gaseous hydrogen from water takes place in a controlled way

The present invention also relates also to a method for the production of gaseous hydrogen starting from water comprising the steps of:

1) providing at least one tablet or at least one device, preferably a cartridge, according to any one of the claims described above;

2) bringing said at least one tablet or said at least one device, preferably said at least one cartridge, into contact with a mass of water;

3) to collect the gaseous hydrogen developed by the reaction with the water.

EXAMPLES

Example 1 ? study of the effect of the degree of compression on the control of hydrogen production

The pads obtained with the process according to the present invention have been tested to evaluate the trend of the speed? of diffusion of the water inside the pads according to the degree of compression of the pads themselves on equal terms? of quantity? and quality? of mechanically activated powder and corresponding quantity? and quality? of mixture of powders used for its production.

Four pellets having the same shape and a height/diameter ratio equal to 0.62, were produced by pressing the same mechanically activated powder (obtained starting from the same initial powder mixture (a)-(c)) but varying the force of compression for each sample as shown in the following table.

Table 1

Figure 1 shows the quantity? of hydrogen (grams) produced over time per kg of mechanically activated powder.

In this figure? also shown is the comparison test carried out using the same mechanically activated powder but in free form (ie not pressed).

As the compression force increases, the speed? of diffusion of the water inside the pad is progressively reduced by decreasing the speed? generation of gaseous hydrogen.

The effect of the compressive force? also clearly visible in the graph shown in Figure 2 where ? reported the time within which 90% of the maximum quantity is reached? of hydrogen generated per kg of mechanically activated powder.

In both figures ? the effect of lengthening the generation times as the force applied for the production of the pads increases and with respect to the free powder is clearly evident.

Example 2 ? study of the effect of the coating of the faces and/or of the variation of the height/diameter ratio of the pads on the control of hydrogen production

The same mixture of powders and relative mechanically activated powder of Example 1? been used to make pressed tablets at the same degree of compression (1.16 kN) in rectangular molds but varying the height/diameter ratio and/or inhibiting one or more? faces of the pads, i.e. by coating with a waterproof coating according to a preferred embodiment of the present invention shown in Figure 3.

The various samples tested are shown in the following table.

Table 2

As ? can be appreciated from the graphs shown in Figure 4, which also shows the comparison test with the mechanically activated powder in free form, variations in the height/diameter ratio and/or inhibition of the faces of the pad, allows to obtain control of the generation of hydrogen over time without the need for any external intervention as would instead happen in the case of free powders.

Example 3 ? study of the influence of the nature of the dust (c) on the production of hydrogen

The mechanically activated powders obtainable with the process according to the present invention have been tested to evaluate the trend of the hydrogen production according to the type of powder (c) used. Different mixtures of powders have been studied according to the present invention in which ? was the powder (c) varied as shown in the following table 3. ? a mixture of comparison powders has also been made in which, instead of the powder (c) according to the present invention ? zinc powder was used.

Each blend of powders ? been charged inside an acoustic resonant mixer according to step (ii) of the process of the present invention, in order to obtain a mechanically activated powder as described in step (iii) of the process according to the present invention. Table 3

For each sample, once the mechanically activated powder according to the process of the present invention has been obtained, ne ? particle size was measured.

The comparison between the granulometric curves shown in Figure 7 (relating to samples 1-4, i.e. samples comprising a salt as powder (c) according to the present invention) and those shown in Figure 8 (relating to the comparison sample, i.e. the sample comprising zinc instead of the powder (c) of the invention), shows how the mechanically activated powders deriving from a mixture of starting powders including salt have a better regularity? in size distribution compared to those resulting from a starting powder mixture including zinc. Furthermore, not only, globally, the first powders appear more? homogeneous, but they also appear to have average dimensions more? contained.

Using the powder mixtures of Table 3 and the relative powders mechanically activated by step (iii) obtained with the process of the invention, tests were carried out in order to measure the evolution of hydrogen.

As shown in Figure 9, the mechanically activated powders according to the present invention deriving from a mixture of starting powders comprising salt show a hydrogen production higher than 90 g per kg of powder and a fraction of hydrogen evolved between 94 and 99%. .

The mechanically activated powders deriving from a mixture of starting powders including zinc, on the other hand, not only develop a quantity? significantly lower hydrogen per kg of powder, but have a yield of less than 85%.

Claims (11)

1. Process for the production of a tablet for the generation of gaseous hydrogen from water including the steps of: (i) make available a blend of powders comprising: (a) between 70% and 99% by mass of an aluminum powder; (b) between 0.5 and 20% by mass of a bismuth powder; (c) between 0.5 and 20% by mass of a powder selected from the group consisting of: a salt powder, a water soluble polymer powder, a sugar powder, or a combination thereof; (ii) loading said mixture of powders into a mixer comprising balls, spheroidal elements, rollers, needle rollers or a combination thereof; (iii) operating said mixer at an acceleration ranging from 50 G to 100 G, preferably for a time ranging from 5 to 300 minutes, preferably interspersing with a number of pauses ranging from 1 to 200, preferably said pauses having a duration of time ranging between 0.5 and 20 minutes each, until a mechanically activated powder is obtained; (iv.a) pressing said mechanically activated powder obtained in step (iii) into a tablet mold by a compressive force of between 0.5 and 150 kN; or (iv.b) inserting said mechanically activated powder obtained in step (iii) into a water-soluble polymer in the molten state and subsequently casting it into a tablet mold or extruding it. 2. Process according to claim 1 wherein: said salt ? selected from the group consisting of: NaCl, KCl, LiCL, CaCl2, YCl3, AgCl2, MgCl2, NH4Cl, and a combination thereof; and/or said water soluble polymer? selected from the group consisting of: polyethyl-2-oxazoline with molecular weight ?500000, preferably ?50000, PEG/PEO with molecular weight ? 1000000, and a combination thereof; and/or said sugar? selected from the group consisting of: a monosaccharide sugar, preferably glucose, a polysaccharide sugar, preferably sucrose, and a combination thereof. 3. Process for making a tablet for the generation of gaseous hydrogen from water in which said tablet comprises at least two layers having two different degrees of compression, said process comprising a step (v) of coupling by compression and/or an adhesive : - at least a first layer obtained by subjecting the mechanically activated powder of step (iii) of the process according to claim 1 or 2 to a step (iv.a?) of pressing said mechanically activated powder in a tablet mold by means of a compressive force between between 0.5 and 80 kN; - with at least a second layer obtained by subjecting the mechanically activated powder of step (iii) of the process according to claim 1 or 2 to a step (iv.a??) of pressing said mechanically activated powder into a tablet mold by means of a force of compression between 80 and 150 kN. 4. Process for making a tablet for the generation of gaseous hydrogen from water in which said tablet comprises at least two layers having different compositions, said process comprising a step (v?) of coupling by compression and/or an adhesive at least two layers obtained according to steps (i)-(iv.a) of the process according to claim 1 or 2 and in which the composition of the powder (c) chosen for said at least one first layer differs from the composition of the powder (c) chosen for said at least a second layer. The process according to claim 4 wherein said at least one first layer and said at least one second layer are obtained by subjecting the mechanically activated powder obtained in step (iii) of the process according to claim 1 or 2 to a step (iv.a?) pressing said mechanically activated powder into a mold for tablets by means of a compressive force of between 0.5 and 80 kN for said at least one first layer and in one step (iv.a??) pressing said mechanically activated powder into a mold for tablets by a compressive force of between 80 and 150 kN for said at least one second layer, or vice versa. 6. Tablet for the generation of gaseous hydrogen from water obtainable with the process according to any one of claims 1-5, optionally coupled with at least one further tablet obtained with the process according to any one of claims 1-5 including step (iv .a) but making available, as an alternative to step (i), a powder or a mixture of inert powders (i.a) chosen from the group consisting of: aluminum oxides, iron oxides, aluminum hydroxides, or a combination thereof. 7. Tablet for the generation of white gaseous hydrogen from water obtained by coupling, by compression and/or an adhesive: - at least a first tablet obtained with the process according to claim 1 comprising step (iv.b); with - at least a second tablet obtained with the process according to claim 1 including step (iv.a) or with the process according to any one of claims 2-5, said pellet for the generation of gaseous white hydrogen from water being optionally coupled with at least one further pellet obtained with the process according to any one of claims 1-5 comprising step (iv.a) but making available, as an alternative to step (i), a powder or a mixture of inert powders (i.a) selected from the group consisting of: aluminum oxides, iron oxides, aluminum hydroxides, or a combination thereof. 8. Tablet according to claim 6 or 7 comprising, on at least one external surface, a waterproof coating preferably selected from the group consisting of: PLA, ABS, PET, PETG or other plastic-based polymers, a phenolic resin, a resin epoxy resin, a polyester resin, a vinyl ester resin, and a combination thereof, and/or having a shape characterized by a height to diameter ratio of between 0.1 and 20. 9. Device comprising a main body defining a containing volume comprising at least one tablet according to any one of claims 6-8, said device being characterized by comprising at least one inlet opening for the water and at least one outlet opening for the gaseous hydrogen produced by said at least one pellet once in contact with said water, said containment volume being shaped in such a way that only one outer surface of said pellet can come into contact with said water. 10. Powder for the generation of gaseous hydrogen from water, obtainable after step (iii) of the process according to claim 1 or 2, said powder being a mechanically activated powder comprising aluminium/bismuth/salt and/or water soluble polymer composite particles and /or sugar depending on the powder chosen (c) in step (i) of said process. 11. Use of the tablet according to any one of claims 6-8 of the device according to claim 9, or of the powder according to claim 10 for the production of gaseous hydrogen starting from water.