PROCEDURE FOR MAKING A CATALYTIC COATING AND CATALYTIC DEVICE FOR HETEROGENEOUS CATALYSIS

Description

PROCEDURE FOR MAKING A CATALYTIC COATING AND CATALYST DEVICE FOR HETEROGENEOUS CATALYSIS DESCRIPTION The project leading to this invention has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 745766. Scope of application The present invention relates to a process for producing a catalytic coating and a catalyst device for heterogeneous catalysis according to the preamble of the respective independent claims. The process and the catalyst device in question are generally included in the industrial sector of the production of catalysts for the chemical industry. More specifically, the catalyst device fits into the sector of the synthesis of organic molecules, particularly polymers, in the chemical industry. The process is therefore advantageously intended to be used to create catalytic coatings on different types of supports, obtaining heterogeneous catalytic devices of different shapes and sizes, intended to be used in chemical reactors for the production of, for example, polymers or other synthetic molecules. State of the art In the production and synthesis of chemical substances, particularly in the production of polymers, the use of catalysts is well known. These are chemical species (e.g., molecules, macromolecules, crystalline materials, or even microorganisms) that participate in a chemical reaction without being consumed by the reaction itself. These species are used to reduce the activation energy required to achieve the chemical reaction between the reactants, which would otherwise occur. - 2 otherwise with very long times, promoting or mediating the transformation between the reagents themselves. More specifically, if the catalysts are in the same phase as the reactants, the catalysis is called “homogeneous”, while if the catalysts are in a different phase than the reactants, the catalysis is called “heterogeneous”. Generally, where possible, heterogeneous catalysis is preferable, as it is not necessary to remove the catalyst from the reaction product between the reactants. In this case, it is known to use metal catalysts generally containing iron, silver, ruthenium, palladium, platinum, gadolinium or rhodium deposited in thin films by cathode pulverization (more commonly called “sputtering”) on support surfaces of catalyst elements inserted into the reactors. The use of catalysts consisting of insulating or semiconducting metal oxides, alone or in combination with electromagnetic waves, such as titanium dioxide, cerium dioxide, zirconium dioxide, aluminum oxide, silica, magnesium oxide, zinc oxide, or nickel oxide, is also known. The heterogeneous catalysts described above have proven to be not free from drawbacks in practice. A first drawback of the heterogeneous catalysts described above is that, although they are suitable for catalyzing a fairly large number of chemical reactions - generally reactions involving the hydrogenation and dehydrogenation of chemical compounds, dehydration, oxidation, cracking of hydrocarbons, alkylation - their use remains limited to polymerization reactions. For example, catalysts based on chromium oxide are mainly known for the polymerization of polyethylene and those based on titanium tetrachloride (but in combination with an organometallic aluminum compound) in the Ziegler-Natta processes for - 3 polymerization of some other polymers. A further drawback of known heterogeneous catalysts is that they are often expensive, especially if made of precious materials (e.g. platinum) or difficult to find, extract and process (e.g. rare earth elements, such as cerium). A further drawback of known heterogeneous catalysts is that they are often unsuitable for the synthesis of enantiomerically pure compounds, i.e., compounds consisting of structurally identical and ideally superimposable molecules. Indeed, these heterogeneous catalysts are unable to selectively catalyze a reaction such that the reactants are transformed into a single stereoisomer of the reaction product. The reaction product is therefore a mixture of stereoisomers that, in most cases (if at all), must be separated using complex and expensive processes. Conversely, in most cases the synthesis of polymers and prepolymers, particularly that of polyurethanes, is aided by homogeneous catalysts. In particular, the most widely used catalysts are generally of the organometallic (or organometallic) type, that is, compounds with the formula Me-R which contain a covalent or ionic bond between a carbon atom (of an alkyl group R) and a metal (Me), such as lithium, magnesium and in some cases sodium, copper and zinc or other transition metals. Other organometallic catalysts have the general formula R-Me-X, where X represents a halogen. In this case, the best-known catalysts include a magnesium atom as the halogen and are known as Grignard reagents. Even the homogeneous catalysts described above have proven to be not free from drawbacks in practice. A first drawback of homogeneous catalysts lies in the difficulty of - 4. Separation of the catalyst from the reaction product. This involves both the risk of product contamination by metals and the impossibility of reusing the entire catalyst, resulting in economic losses. In particular, the problem of contamination is particularly acute in the pharmaceutical industry, where the purities of compounds must be extremely high. A further drawback of known homogeneous catalysts is that the residue present in the finished product continues to interact with the product itself, leading to unwanted side reactions. For example, the catalyst residue present in polyurethane prepolymers used to produce instant spray foams promotes the crosslinking process of the prepolymer inside the container, deteriorating the product and resulting in a limited shelf life. This process, which naturally occurs very rapidly when the prepolymer is exposed to air humidity, i.e., when it is used, would be extremely slow inside the container if the catalyst were not present. A further drawback of known homogeneous catalysts is that they do not allow for continuous synthesis processes and therefore do not allow for obtaining lower or higher quantities of product than those dictated by the size of the chemical reactor in which they are used. A further drawback of known homogeneous catalysts is the difficulty of disposal, due to the presence of metals within them that cannot be released into the environment. There is therefore a keenly felt need in the sector to find an alternative to the organometallic catalysts used in homogeneous catalysis for the synthesis of various chemical compounds, which however does not present the disadvantages of known heterogeneous catalysts. - 5 Presentation of the invention In this situation, the problem underlying the present invention is therefore to overcome the drawbacks manifested by the above-mentioned known solutions by providing a process for producing a catalytic coating and a catalyst device for heterogeneous catalysis, which allow for the simple production of catalyst devices with a high specific surface area capable of being used in chemical reactors operating with heterogeneous catalysis. A further aim of the present invention is to provide a catalyst device for heterogeneous catalysis, which allows the replacement of industrial processes, currently carried out in homogeneous catalysis, with processes that can be carried out in heterogeneous catalysis. A further object of the present invention is to provide a process which allows for the production of a catalytic coating which is versatile in use. A further object of the present invention is to provide a process which allows to obtain a catalytic coating suitable for the heterogeneous catalysis of a reaction. A further object of the present invention is to provide a catalyst device which can be used in a continuous process. A further object of the present invention is to provide a process and a catalyst device which are simple and economical to manufacture. Brief description of the drawings The technical characteristics of the present invention, according to the above-mentioned purposes, can be found in the contents of the claims reported below and the advantages of the same. - 6 will be more evident in the detailed description that follows, made with reference to the attached figures, which represent a purely exemplary and non-limiting embodiment in which: - Figure 1 shows a sectional view of an example of a plasma generating device that can be used to carry out the process in question; - Figure 2 shows a perspective view of a laminar substrate coated with a catalytic coating obtained with the subject process, which substrate can be used to make a catalytic device; - Figure 3 shows a perspective view of the substrate of Figure 2 wound in a spiral shape; - Figure 4 shows a perspective view of a catalyst device in the form of a cartridge comprising the substrate of Figure 3; - Figure 5 shows a perspective view of a substrate in the form of a helical impeller. Detailed description of some favorite examples of realization With reference to the attached drawings, the reference numeral 1 indicates as a whole a catalytic coating obtainable with the process which is the subject of the present invention. The process for producing a catalytic coating 1 is advantageously intended for the production of coatings with catalytic functionality for the chemical industry, in particular for heterogeneous catalytic devices used within chemical reactors. Furthermore, the process of the invention is advantageously intended for use in the production of catalytic devices 100 of various shapes and sizes and with high specific surface areas, for the heterogeneous catalysis of various chemical reactions, particularly polymerization. More specifically, the catalyst device 100, preferably obtained by the process of the invention, is advantageously intended to be - 7 used in the chemical and pharmaceutical industry for the synthesis of chemical compounds. In accordance with the idea underlying the present invention, the process for producing a catalytic coating 1 comprises a step of preparing a plasma generation device 2. Such plasma generation device 2 comprises an ionization duct 3, which extends between an inlet section 31 and an outlet section 32, and at least one electromagnetic field generator 4 arranged at a portion of the ionization duct 3. In particular, the electromagnetic field generator 4 can be of any type suitable for generating plasma. For example, the electromagnetic field generator 4 can be powered by a direct current (DC) source, alternating current with radio frequencies (RF, from 3 kHz to 300 GHz, especially high-frequency alternating current, HF), or by pulsed and microwave sources. In accordance with an embodiment illustrated in figure 1, the ionization duct 3 of the plasma generation device 4 comprises a first tubular body 33 made of dielectric material. The electromagnetic field generator 4 advantageously comprises a first annular electrode 41 and a second annular electrode 42 intended to be polarized at High Frequency (HF). In particular, the first and second annular electrodes 41, 42 are arranged one after the other, coaxially, around the first tubular body 33 and one of the first and second annular electrodes 41, 42 is grounded while the other is intended to be energized. Furthermore, the electromagnetic field generator 4 advantageously comprises a third annular electrode 43 intended to be polarized at Radio Frequency (RF), which is arranged in correspondence with the output section 32 of the ionization duct 3. - 8 Advantageously, the plasma generation device 2 further comprises an evaporation chamber (not shown in the attached figures), in fluid communication with the inlet section 31 of the ionization duct 3. According to the invention, the preparation step further provides for the preparation of a substrate 10, which is arranged in correspondence with the outlet section 32 of the plasma generation device 2 and is equipped with a support surface 11 facing the aforementioned outlet section 32. Advantageously, the substrate 10 is made of at least one material selected from metallic, polymeric or ceramic materials. Furthermore, the preparation step involves the preparation of a non-metallic organic catalyst precursor, preferably a volatile precursor. The term “non-metallic organic catalyst” refers to an organic compound free of metal atoms that has catalytic functionality, i.e., is intended to take part in a pre-established chemical reaction to increase the reaction rate without being consumed by the reaction itself. The term "precursor" refers to any organic molecule containing substantially the same atoms or groups of atoms as the nonmetallic organic catalyst, which can be transformed into a compound with catalytic functionality. The precursor may already be a molecule with catalytic functionality or an inert molecule or solvent. Advantageously, during the preparation phase, the precursor is placed inside the evaporation chamber at least partially in the liquid or gaseous phase. For example, the precursor is a volatile precursor, which is in gas or vapor form at room temperature and pressure. Alternatively, the precursor can be a liquid or a solid, pure or mixed with a - 9 solvent, which is brought into the gas or vapor phase inside the evaporation chamber by decreasing the pressure, for example by applying a vacuum, and / or by increasing the temperature. According to a particular embodiment, the preparation phase involves placing the liquid-phase precursor and a carrier gas inside the evaporation chamber, such as air, helium, hydrogen, neon, nitrogen, argon, oxygen, or mixtures thereof, which is bubbled through the liquid-phase precursor. Advantageously, the carrier gas then mixes with the precursor vapors, carrying it along. In accordance with a further embodiment, the liquid-phase precursor is nebulized inside the carrier gas, obtaining a two-phase aerosol. According to the invention, the process comprises a feed step, in which the precursor is fed into the ionization conduit 3 via the inlet section 31. Advantageously, in the feed phase, the precursor is transported from the evaporation chamber to the ionization duct 31, for example, by means of the carrier gas. According to the invention, the process further comprises an ionization phase, in which the electromagnetic field generator 4 generates an electromagnetic field that interacts with the precursor in the ionization duct 3 and ionizes the precursor. In this way, the magnetic field generator 4 produces ionized precursor fragments 5. The term "ionized fragments" refers to portions of the original precursor molecule to which electrons are advantageously added or removed and / or which, through ionization, are advantageously separated from each other, breaking the covalent bonds between one or more atoms. In particular, the ionized fragments 5 can - 10 be single atoms or groups of atoms (including the entire precursor). According to the invention, the process further comprises a coating step, in which the ionized precursor fragments 5 exit from the outlet section 32 of the ionization conduit 3 and are applied to the support surface 11 of the substrate 10, and in which the ionized fragments 5 react with each other to form at least one plasma polymer with catalytic functionality. In particular, the plasma polymer forms, at least partially, a catalytic coating 1 on the support surface 11. In particular, at the outlet section 32 of the ionization duct 3, negatively ionized fragments (anions), positively ionized fragments (cations), free electrons, radicals and / or intact precursor may be found. In more detail, the ionized precursor fragments 5 advantageously comprise ionized monomer units that recombine with each other on the substrate 10 to form the polymer plasma. In this way, a catalytic coating 1 is advantageously obtained by plasma deposition, in which the catalytic coating 1 contains a plasma-polymer with catalytic functionality. This process is easy to implement and allows the creation of catalytic devices 100 with a high specific surface area capable of being used in chemical reactors operating with heterogeneous catalysis, for example in the polymer or pharmaceutical industries. Furthermore, it was surprisingly found that this process can utilize both precursors that do not possess catalytic functionality per se and precursors that are generally used as homogeneous-phase catalysts. It is also possible to use a mixture of precursors of the two different types. Advantageously, the precursor comprises at least one atom chosen from: nitrogen, sulfur, oxygen. In particular, this atom in the ionization phase and in the - The coating is contained in one of the ionized fragments 5. Therefore, this atom is also contained in the plasma polymer. Advantageously, this atom in the plasma polymer has at least one free electron pair, i.e., one not involved in a bond with other atoms. Among the atoms mentioned above, it is preferable that the precursor contains at least nitrogen or sulfur and in particular the best results were obtained with precursors containing at least nitrogen. In accordance with a preferred embodiment of the invention, the precursor and / or plasma polymer comprises at least one nitrogenous functional group. Specifically, the precursor and / or plasma polymer are advantageously selected from the following groups of organic compounds: amines, heterocyclic amines, amides, imides, imines, nitriles and isonitriles, and silazanes. Preferably, the plasma polymer is a tertiary amine comprising at least one -NR2 functional group, a secondary amine comprising at least one -NHR functional group, or a primary amine comprising at least one -NH2 functional group, where R is an alkyl group, preferably a methyl group. This plasma polymer can be advantageously obtained starting from one of the above-mentioned precursor groups. For example, the precursor is selected from a compound of the group comprising: dimethylaminoethanol, bis(dimethylammonium)dimethylsilane, N,N,N '-trimethyl-N '-hydroxyethylbisaminoethyl ether, N-(3-dimethylaminopropyl)-N,N-diisopropanolamine (DPA), N,N-bis(3-dimethylaminopropyl)-N-isopropanolamine, 1,3-propanediamine, N'-(3-(dimethylamino)propyl)-N,N-dimethyl, 2-(2-dimethylaminoethoxy)ethanol, N,N,N'-trimethylaminoethylethanolamine, dimethylaminopropylamine (DMAPA) and their isomers. - 12 In accordance with a further embodiment of the invention, the precursor and / or plasma polymer comprises at least one sulfur-containing functional group. In particular, the precursor and / or plasma polymer are advantageously selected from the following groups of organic compounds: thiols, mercaptans, sulfides, disulfides, sulfones, sulfoxides, sulfonic acids, and sulfinic acids. In order to improve the adhesion of the catalytic coating 1 to the support surface 11 of the substrate 10, particularly if the latter is made of metal, the plasma polymer comprises at least one siloxane group. In particular, the aforementioned siloxane group chemically bonds to the support surface 11 of the substrate 10 during the coating step. More specifically, the siloxane group is advantageously present in the precursor. Furthermore, in the ionization phase and in the coating phase, this siloxane group is advantageously contained in at least one of the ionized fragments 5. Advantageously, the catalytic coating 1 is equipped with catalytic functionality for a chemical reaction selected from: synthesis reactions of urethane prepolymers and / or polymers, synthesis reactions of isocyanurate prepolymers and / or polymers, polycondensation reactions, polymerization reactions catalyzed by Bronsted bases, synthesis reactions of thermosetting resins. Advantageously, the process also includes an ignition phase, in which an activation gas, preferably argon, is introduced into the ionization conduit 3 at least in correspondence with the electromagnetic field generator 4, for example in correspondence with one of the annular electrodes 41, 42, 43, and the electromagnetic field interacts with the activation gas, ionizing it. In this way, the electromagnetic field brings the activation gas into a plasma state. Advantageously, furthermore, in the ionization phase, the precursor is introduced into the gas - 13 activation in plasma state to generate the ionized precursor fragments 5. In particular, the priming phase is advantageously performed before the ionization phase. In accordance with the embodiment illustrated in figure 1, the ionization duct 3 of the plasma generation device 2 comprises at least a second tubular body 34 and preferably also a third tubular body 35 arranged inside such second tubular body 34, and preferably both arranged inside the first tubular body 33. Advantageously, the precursor is transported in the gaseous phase or as an aerosol inside the second tubular body 34, and the activation gas is transported in the annular volume between the first tubular body 33 and the second tubular body 34. In accordance with an embodiment variant, the precursor is transported in liquid form inside the third tubular body 35 and the carrier gas in the annular volume between the second tubular body 34 and the third tubular body 35 and the second and third tubular ducts 34, 35 end in correspondence with the electromagnetic field generator 4, in particular advantageously in correspondence with one of the annular electrodes 41, 42, 43 of the electromagnetic field generator 4. Advantageously, therefore, in the feeding phase the precursor can be transported in liquid form inside the carrier duct 3 and nebulized when it meets the carrier gas at the end of the third tubular body 35 in correspondence with the electromagnetic field generator 4. Subsequently, at the exit of the second tubular body 34, the nebulized precursor advantageously meets the activation gas in the plasma phase and is ionized. According to this embodiment of the invention, the precursor meets the gas - 14 plasma state activation at the exit of the first tubular body 34 shortly before the exit section 32. At that point, the precursor advantageously reacts with the plasma state activation gas, being fragmented and ionized, and then reorganizing and polymerizing on the support surface 11. According to one possible operating situation, the precursor is not in plasma state and the ionized fragments 5 are produced by the ionized activation gas and are transported by it to the support surface 11 where they react and recombine with each other. According to a further operating situation, the magnetic field generator 4 brings the precursor into a plasma state (with or without the activation gas trigger) containing the ionized precursor fragments 5. Obviously, without thereby departing from the scope of protection of the invention, at least one of the first, second and third tubular bodies 33, 34, 35 of the ionization duct 3 can be separated from the others and can intercept them at the electromagnetic field generator 4. Furthermore, the ionization duct 3 can be of any size and shape, for example with a circular, rectangular or square cross-section. Advantageously, the process comprises a movement step, during the coating step, in which the plasma generation device 2 and / or the substrate 10 are moved relative to each other along a direction parallel to the support surface 11 of the substrate 10 to successively treat uncoated areas of the support surface 11 itself. In accordance with a variant embodiment of the process, the preparation phase of the substrate 10 involves producing the aforementioned substrate 10 using a 3D printer, for example of the FDM (Fused Deposition Modelling) type, equipped with at least one dispensing nozzle. - 15 Advantageously, in the preparation phase the printer's dispensing nozzle 3D is actuated to move along a build path to dispense a base material along the build path to form the substrate 10. Specifically, the substrate preparation phase involves using a 3D printer, of a known type, equipped with a nozzle heated to a predetermined temperature, in which a through-hole is machined, and a base material wire passing through the through-hole. Advantageously, the base material is capable of melting at the aforementioned temperature of the nozzle and is preferably a thermoplastic polymer, such as ABS. Advantageously, in the coating step, the plasma generation device 2 is moved simultaneously with the dispensing nozzle of the 3D printer, so that the outlet section 32 of the ionization duct 3 follows the dispensing nozzle to deposit the catalytic coating 1 on at least a part of the base material dispensed from the dispensing nozzle along the generation path, in particular on the base material constituting the support surface 11 of the substrate 10. More specifically, the substrate preparation phase 10, specifically through 3D printing, occurs simultaneously with the handling phase and the coating phase. Specifically, during the handling phase, the plasma generation device 2 is moved to a predetermined distance from the 3D printer's movement nozzle with a time lag. In this way, the catalytic coating 1 is created on the support surface 11 during the latter's production. Advantageously, each of the above process steps can be carried out at atmospheric pressure or under vacuum conditions. Furthermore, the process steps are preferably carried out continuously until - 16 complete coating of the support surface 11 of the substrate 10. The present invention also relates to a catalyst device 100 for heterogeneous catalysis, advantageously obtained by means of the process described above, the references of which will be retained for simplicity of exposition. According to the invention, the catalyst device 100 for heterogeneous catalysis comprises a substrate 10 provided with a support surface 11 and a catalytic coating 1, fixed to the support surface 11. Advantageously, the substrate 10 is made of at least one material selected from metallic, polymeric or ceramic materials. In accordance with the idea underlying the present invention, the catalytic coating 1 comprises at least one non-metallic organic catalyst in the form of a plasma-polymer chemically bonded to the support surface 11. Advantageously, the catalytic coating 1 is obtained by plasma deposition starting from an organic catalyst precursor, preferably using the process described above. In particular, the plasma deposition can be atmospheric plasma vapor deposition (APVD), atmospheric plasma liquid deposition (APLD), or plasma enhanced chemical vapor deposition (PECVD). In accordance with a preferred embodiment of the invention, the plasma-polymer advantageously comprises at least one atom selected from nitrogen, sulfur, or oxygen. Advantageously, this atom in the plasma-polymer has at least one free electron pair, i.e., one not bonded to other atoms. Preferably, the plasma polymer of the catalytic coating 1 is an amine. Preferably, furthermore, the plasma polymer comprises at least one nitrogenous group of - 17 generic formula -NR2 (tertiary amine), -NHR (secondary amine) or -NH2 (primary amine), where R is an alkyl group, preferably methyl. In order to improve the adhesion of the catalytic coating 1 to the support surface 11 of the substrate 10, particularly if the latter is made of metal, the plasma polymer comprises at least one siloxane group. In particular, the aforementioned siloxane group is chemically bonded to the support surface 11 of the substrate 10 during the coating step. Advantageously, therefore, the plasma polymer is an aminosiloxane. The catalyst device 100 can be made in various shapes and sizes, depending on the specific application destinations. For example, the catalyst device 100 can be made in the form of a tubular cartridge for a continuous heterogeneous catalysis reactor, as illustrated in Figure 4. In this case, the substrate 10 is advantageously equipped with a spiral-shaped body, equipped with the support surface 11 on which the catalytic coating 1 is arranged. Alternatively, the substrate 10 can also be equipped with a helical-shaped body. Furthermore, the catalyst device 100 advantageously comprises a tubular containment chamber 6, which extends between an inlet port 61 for the entry of a flow of at least one reagent and an outlet port 62 for the exit of a reaction product. The substrate 10 in the form of a spiral with the catalytic coating 1 is advantageously intended to be inserted inside the containment chamber 6 to catalyze a chemical reaction capable of transforming the reagent (or reagents) into the reaction product. For example, the catalytic coating 1 is equipped with catalytic functionality for a chemical reaction selected from: synthesis reactions of urethane prepolymers and / or polymers, synthesis reactions of isocyanurate prepolymers and / or polymers, - 18 polycondensation, polymerization reactions catalyzed by Bronsted bases, synthesis reactions of thermosetting resins. Obviously, without departing from the scope of the invention, the catalyst device 100 can be made in other forms. For example, in an embodiment not illustrated, the catalyst device 100 is made in the form of an impeller for a chemical reactor, i.e., by coating the impeller with the catalytic coating 1, so that the reaction between the reactants is catalyzed when they come into contact with the impeller. A first embodiment of a catalyst device 100 according to the invention is described below. In accordance with the first embodiment, a sheet-shaped substrate 10 made of AISI 301 steel was subjected to atmospheric pressure plasma deposition treatment according to the procedure described above. The sheet-shaped substrate 10 was treated on both support surfaces 11 with a plasma generator 4 power of 40 W at a treatment rate of 8 cm2 / min. Dimethylaminoethanol in vapor phase at atmospheric pressure was used as the precursor. The plasma was activated with argon. A substrate 10 with a catalytic coating 1 was then obtained, schematically illustrated in Figure 2. It was observed that the catalytic coating 1 thus obtained is equipped with -N(CHs)2 functional groups, which act as a catalytic site. Subsequently, the substrate 11 with catalytic coating 1 was shaped into a spiral and inserted into a tubular containment chamber 6, as illustrated in Figures 3 and 4. A second embodiment of a catalyst device is described below. - 19 100 according to the invention. In accordance with the second embodiment, a sheet-shaped substrate 10 made of AISI 301 steel was subjected to atmospheric pressure plasma deposition treatment according to the procedure described above. The sheet-shaped substrate 10 was treated on both support surfaces 11 with a plasma generator 4 power of 30 W at a treatment rate of 8 cm2 / min. Bis(dimethylamino)dimethylsilane was used as a precursor in the vapor phase at atmospheric pressure. The plasma was activated by argon. A substrate 10 with a catalytic coating 1 was then obtained. Again, it was observed that the catalytic coating 1 thus obtained is equipped with -N(CHs)2 functional groups, which act as a catalytic site. Furthermore, improved adhesion of the catalytic coating 1 on the metal support surface 11 was observed, due to the presence of siloxane groups in the polymer plasma. Subsequently, the substrate 10 with catalytic coating 1 was shaped into a spiral and inserted into a tubular containment chamber 6, as shown in the first embodiment. A third embodiment of a catalyst device 100 according to the invention is described below. In accordance with the third embodiment, a laminar-shaped substrate 10 made of AISI 301 steel was subjected to atmospheric pressure plasma deposition treatment according to the procedure described above. The laminar-shaped substrate 10 was treated on both support surfaces 11 with a plasma generator 5 power of 50 W at a treatment rate of 1 m2 / h. 3-methyl-thiophene in vapor phase at atmospheric pressure was used as the precursor. - 20 atmospheric pressure. The plasma was activated by argon. This resulted in a substrate 10 with a catalytic coating 1. In this case, it was observed that the thus obtained catalytic coating 1 is equipped with sulfur-containing functional groups (-SR2, -SRH) which act as a catalytic site. Subsequently, the substrate 10 with catalytic coating 1 was shaped into a spiral and inserted into a tubular containment chamber 6, as indicated in the first embodiment. A fourth embodiment of a catalyst device 100 according to the invention is described below. The fourth embodiment involves the use of a laminar-shaped substrate 10 made of anodized titanium. This substrate was subjected to a plasma-assisted deposition treatment using hexamethyldisilazane vapors as a precursor. A substrate 10 was then obtained with a catalytic coating 1. It was observed that the catalytic coating 1 thus obtained is equipped with nitrogen-containing functional groups (-NH2, -NHR, -NR2), which act as a catalytic site. Furthermore, improved adhesion of the catalytic coating 1 to the metal support surface 11 was observed, due to the presence of siloxane groups in the polymer plasma. Subsequently, the substrate 10 with the catalytic coating 1 was shaped into a spiral and inserted into a tubular containment chamber 6, as shown in the first embodiment. A fifth embodiment of a catalyst device 100 according to the invention is described below. The fifth embodiment involves using the plasma generation device 2 described above and illustrated in figure 1 as an additional module for FDM 3D printers. - 21 In particular, a substrate 10 in the shape of a helical impeller, illustrated in Figure 5, was 3D printed in polymeric material, specifically ABS. During the production of this impeller, which occurs by printing ABS layer by layer, the plasma generation device 2 intervened, after printing each single layer of ABS, to functionalize the newly printed surface. For this deposition treatment according to the process, dimethyl-amino-ethanol was used as a precursor, and a substrate 10 with a catalytic coating 1 was thus obtained. It was observed that the catalytic coating 1 thus obtained is equipped with nitrogen-containing functional groups (-NH2, -NHR, -NR2), which act as a catalytic site. The substrate 10 was made of suitable dimensions to be inserted into a tubular containment chamber 6, as in the first embodiment. Each catalyst device 100 obtained according to each embodiment described was tested to catalyze a synthesis reaction of a urethane prepolymer of the type that can be introduced into spray cans to obtain polyurethane foam. It was observed that, in all of the aforementioned first, second, third, fourth, and fifth embodiments, the catalyst device 100 has good catalytic functionality without the catalyst remaining within the prepolymer. Furthermore, the shelf life of the prepolymer thus obtained before being used is longer, in the absence of homogeneous catalysts that are not removed after the prepolymer synthesis reaction. The invention thus conceived therefore achieves the intended purposes.

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