PL244205B1 - Nickel-vanadium catalyst for carbon dioxide valorization, method of obtaining a nickel-vanadium catalyst and the use of nickel-vanadium catalyst in carbon dioxide valorization processes - Google Patents

Abstract

The first subject of the invention is a nickel-vanadium catalyst on a solid support, characterized in that the weight ratio of nickel to vanadium in the catalyst is from 1 to 25, with the vanadium being deposited on the solid support in the form of nickel oxide crystallites and/or vanadium oxide crystallites and /or crystallites of mixed oxides of nickel and vanadium, the support being obtained from a precursor with a hydrotalcite structure. Another subject of the invention is the method of obtaining the catalyst and its use in carbon dioxide valorization processes.

Description

Description of the invention

The first subject of the invention is a nickel-vanadium catalyst on a solid support for the valorization of carbon dioxide. The second subject of the invention is a method for obtaining a nickel-vanadium catalyst. Another subject of the invention is the use of a nickel-vanadium catalyst on a solid support in carbon dioxide valorization processes, especially in carbon dioxide hydrogenation processes or carbon dioxide reforming of alkanes.

State of the art

Preventing or reducing the effects of climate change is a key priority for the European Union (EU). The EU is committed to reducing greenhouse gas emissions by 20% by 2020 and 40% by 2030 compared to 1990 levels. As a result, a number of actions are being taken to promote renewable energy, energy efficiency and low-carbon technologies, including including technologies for the use of anthropogenic carbon dioxide (CO2) (carbon dioxide utilization technologies CDUt). Among CDUt technologies, the catalytic conversion of CO2 to hydrocarbons through hydrogenation enables the use of CO2 to produce valuable chemicals/energy carriers and simultaneously reduce CO2 emissions[1]. Almost 90% of research contributions over the last five years are devoted to the development of an active, durable and stable catalyst for use as a catalyst with high selectivity and durability in downstream industrial processes [1-3].

Catalytic conversion of light alkanes by reforming with carbon dioxide, CO2 (dry reforming, DR) enables the use of, for example, natural gas to produce synthesis gas with an H2/CO ratio close to one. This reaction proceeds according to equation (1):

CH ₄ +CO ₂ = 2CO+2H ₂ ΔΗ= - 241 kJ/mol (1) and enables the reduction of emissions of harmful greenhouse gases, such as CO2 and ChU [4-5]. The reaction of alkanes with carbon dioxide is an endothermic reaction, and compared to steam reforming, whose ΔΗ = - 2405 kJ/mol, proceeds slower and requires approximately 15% more heat. This process is also exposed to the formation of carbon deposits (coke), while it enables the valorization of two harmful greenhouse gases to produce valuable products, i.e. syngas, for further inorganic (e.g. ammonia) and organic (e.g. alcohols, ethers, aldehydes, fuels) syntheses synthetic). In addition to the main high-endothermic reaction of converting methane into carbon dioxide (Equation 1), the following reactions (2)-(5) take place in the process:

CH ₄ =C+2H ₂ ΔΗ ₂ 98Κ ⁼ -241 kJ mol ¹ (2) 2CO=C+ _CO2 ΔΗ ₂ 98Κ = +75 kJ mol ¹ (3) CO ₂ + H ₂ = CO + h ₂ o ΔΗ ₂₉ 8Κ = -40 kJ mol ¹ (4) C + Η2θ( _β )=CO + H2 ΔΗ ₂ 98Κ = -131 kJ mol ¹ (5)

Reforming of natural gas with carbon dioxide can be carried out in a tubular reformer, similarly to conventional steam reforming, to produce a mixture of raw syngas with the composition CO = 48, H2 = 44, ChU = 4, CO2 = 2, H2O = 2 (%) [5 -7]. Conversion of natural gas (methane, ChU) with carbon dioxide is a very promising process in the face of sustainable development, because it involves a reaction between CO2 and ChU; which are classified as greenhouse gases and dry reforming may play a significant role in reducing this effect. In addition to methane, reforming uses hydrocarbons such as alcohols, aldehydes, ketones and acids, which in their structural structure contain oxygen as a heteroatom. These hydrocarbons can be obtained by processing chemical or biochemical biomass, including waste biomass, and their origin can be considered renewable [4-9].

There are known nickel catalysts and those based on noble metals that are used in reforming processes [1-6]. The most commonly used dry reforming catalysts are nickel (Ni) catalysts, which tend to deactivate due to metal sintering and high soot (coke) formation rates [1-5] [6-9]. Noble metals such as Pt, Rh, Ru and Ir present stable activity with low rates of soot formation and deposition on the catalyst during the reaction, but their high cost and limited availability make them unattractive in comparison

PL 244205 Β1 with catalysts based on base metals [5,10-13]. Dry reforming and effective CO2 valorization by reforming therefore require the use of stable and effective catalysts resistant to coking. Therefore, many studies currently conducted are focused on the search for an economical, durable and active catalyst, the activity of the base metal in activating the C-0 and C-H bond, resistance to coke formation and the type of support in order to improve the efficiency of the catalyst [3, 11].

Copper catalysts are also known in the processes of reforming oxidized hydrocarbons. A significant drawback hindering the use of copper catalysts in the reforming processes of hydrocarbons containing oxygen, i.e. ethers, alcohols, acids, ketones, e.g. dimethyl ether (DME), diethyl ether (DEE), is their high susceptibility to thermal deactivation [10-13]. For this reason, research work is focused on searching for catalytic systems characterized by high and at the same time stable activity in a temperature range that is interesting from a technological point of view - currently, for platinum catalysts with the addition of germanium, iridium or rhenium supported on a-AEOs, the temperature is in the range of 480-550 °C for pressure in the range of 0.35-3 MPa. The proposed spinel systems, e.g. CuFe2O4, or catalytic materials based on nickel deposited on simple ones, e.g. N1/Al2O3, or mixed oxide systems (CeZrO2) + Ni/Al2O3, are also tested in the aspect of ether reforming, while coking is problematic in the dry reforming system catalyst [12-14]. The advantage of nickel catalysts over other systems in terms of use in reforming processes is due to their high selectivity to H2, high thermal stability, relatively simple preparation and lower price compared to catalysts based on noble metals. These advantages are particularly pronounced in the case of high-temperature alkane reforming processes on catalysts containing noble metals (Garcia-Dieguez, M. Improved Pt-Ni nanocatalysts for dry reforming of methane, Applied Catalysis A: General Volume 377, Issue 1-2, 2010, Pages 191-199; Garcia-Dieguez, M. Nanostructured Pt- and Ni-based catalysts for CO2 - reforming of methane, Journal of Catalysis Volume 270, Issue 1,2010, Pages 136-145) and DME, which are proposed for combined processes with fuel cells (P. Kowalik et.ai Biofuel steam reforming catalyst for fuel cell application; Catalysis Today Volume 254, 1 October 2015, Pages 129-134). Additionally, N1/Al2O3 catalysts obtained by multi-stage impregnation are successfully used in hydrocarbon steam reforming processes (P. Kowalik et.a. Biofuel steam reforming catalyst for fuel cell application; Catalysis Today Volume 254, 1 October 2015, Pages 129-134).

One of the problems associated with the operation of nickel catalysts on oxide supports may be the deposition of carbon deposits. The search for catalysts with high resistance to carbonization is one of the key problems in the future processes of obtaining hydrogen from hydrocarbons through various variants of reforming [5-14]. In the light of literature reports, two ways of modifying catalysts dominate: by increasing the alkalinity of the support (the deposit precursor is formed on the acid centers of the support) or by doping the catalyst surface with oxygen-rich compounds, the mechanism of action of which is based on the surface oxidation of deposit nuclei. Some metal oxides seem interesting in this respect, especially V ₂ O ₅ which exhibits catalytic oxidizing properties [7-8]. Therefore, a Ni catalyst containing vanadium in its composition, in the form of vanadium (V) oxide V2Os, was developed; which is the subject of the current patent application.

The CO2 hydrogenation reaction (methanation) proceeds according to equation (6):

CO ₂ + 4H ₂ = CH ₄ + 2H ₂ O, AH _29SK = -165 kJ mol· ¹ (6), is highly exothermic. Moreover, pressure and temperature significantly affect the equilibrium of the reaction. According to thermodynamics, to achieve high CO2 conversion, the reaction must be carried out at a low temperature. However, low temperature means slow reaction kinetics and low CO2 conversion, especially below 523 K. On the other hand, a decrease in methane yield above 723 K is observed, which is accompanied by the formation of CO as a by-product through the reverse conversion of carbon monoxide with water vapor, i.e. reverse watergas shift reaction (RWGSR). High temperature also leads to deterioration of the catalyst properties by sintering.

In recent years, numerous studies have been conducted on CO2 methanation catalysts. Almost 90% of research contributions over the last five years have been devoted to developing an active, highly durable and stable catalyst suitable for use in the hydrogenation of CO2 to methane. Among them, Ni-based catalysts are the most studied material due to their relatively high activity and low cost. Typically, however, in the tested systems the conversion obtained does not exceed 50% and the catalysts tend to be deactivated during the reaction time of up to 60-120 minutes. However, the use of a catalyst in industrial installations requires a catalyst that exhibits stable activity.

Current research on CO2 valorization and reintroduction of waste carbon dioxide into the chain of valuable products mainly concerns the development of a stable catalyst for this process. The process of reducing CO2 to methanol is a known and used process. In the technology used by BASF, the process takes place in the liquid phase at a temperature of 80°C, a pressure of 4.5 MPa and the use of NaOCH3. The obtained methanol is obtained by reacting and recirculating methyl formate, and the main product of the process is formic acid. Conventional CO2 hydrogenation processes to methanol involve catalytic conversion on copper-zinc mixed oxide (Cu-Zn) catalysts at high operating temperatures (230-270°C), where the production of methanol is thermodynamically unfavorable due to the exothermic nature of the reaction. However, the improvement in catalyst performance was limited under these conditions. Behrens, M., et al. Science 2012, 336, 893. Moreover, the reduction of CO2 to methanol is a six-electron process, and the use of a single catalyst to obtain good efficiency is insufficient. The developed nickel-vanadium catalysts for renewable methane synthesis and subsequent methane reforming in the same systems, also using carbon dioxide, assume the conversion of CO2 derivatives such as carbonates, carbamates and formates to methane.

Nickel catalysts are known to be used in both reforming and hydrogenation processes of carbon dioxide. Research on catalyst activity, stability and resistance to carbon formation is usually carried out by adding promoters, depositing the active phase on various supports or using various methods of catalyst preparation.

Among the promoters, cerium (Ce) is often used to improve the dispersion of Ni nanoparticles and reduce the size of Ni particles. The optimal content of cerium oxide in the catalyst also leads to effective activation of CO2 through the Ce ³ 7Ce ⁴⁺ ion pair. Another way to increase catalytic efficiency can be achieved by involving plasma in the catalytic process. Combining a dielectric barrier plasma (DBD) with a catalyst can initiate chemical reactions such as ionization, excitation, and dissociation at lower temperatures. On the other hand, it can also have an additional influence on the physicochemical properties of the catalyst, such as the dispersion of the active site, the number of available active sites, etc. In fact, these properties of the catalyst are directly related to the activity of the catalyst, selectivity and the amount of activated/converted CO2, since there is a lot of CO2 in the plasma. active particles such as electrons, ions and radicals, which may unfortunately promote the coking of the catalyst. Additionally, the known method of producing a Ni-Ce catalyst requires the use of Ce solutions, which is harmful to health. Despite the use of Ce, soot release is still observed on the catalysts, especially at high temperatures, which adversely affects the activity of the obtained catalytic layers and leads to catalyst poisoning. This leads to a loss of the number of catalytically active sites in a given process or to a change in the desired reaction path to obtain the desired product and a reduction in the efficiency of the catalyst.

Vanadium or nickel-vanadium catalysts are known from the scientific literature. The US patent application US3182027A describes a catalyst containing V2O5 dispersed in potassium glass. It is used in the oxidation of polycyclic aromatic hydrocarbons, especially the oxidation of naphtha from toluene to phthalic anhydride. According to the solution described therein, a solution of vanadium pentoxide and molten potassium metabisulfate is used in a molar ratio of K2O:V2O5 between 1:1 and 6:1, preferably about 4:1. The solution is left to cool and harden. Another US patent application US3277017A discloses a solid-supported vanadium catalyst (porous alumina) containing silver phosphate for the oxidation of gaseous organic compounds to dicarboxylic acid, maleic and phthalic anhydrides. According to the cited solution, the share of V2O5 in the catalyst composition was not less than 20% in order to visibly improve the activity. Another American patent application US20130244115A1 presents a method of forming thin layers in the form of a rhombohedral V2O5 film. It also discloses a description of a battery containing the above-mentioned. films as cathode materials. The scientific publication Dehydrogenation of isobutane over V2Os/a-Al2O3 catalyst (React.Kinet.Catal.Lett. Vol. 74, No. 1, 103-110) describes the preparation of a vanadium catalyst by impregnation of a-Al2O3 or SiO2 with a NH4VO3 solution. The same publication also describes the use of this catalyst in the isobutane dehydrogenation reaction. However, in the publication Effect of additives on properties of V2Os/SiO2 and V2Os/MgO catalysts: I. Oxidative dehydrogenation of propane and ethane (Applied Catalysis A: General 309 (2006) 10-16), heterogeneous catalysts containing vanadium (V) oxide are presented. on silica or magnesium oxide obtained by impregnating carriers with a solution containing NH4VO3. It describes a catalyst tested in the oxidative dehydrogenation of ethane and propane. In turn, in the publication Hydrogen production by steam reforming of DME over Ni-based catalysts modified with vanadium (International Journal of Hydrogen Energy, Volume 41, Issue 43, 16 November 2016, Pages 19781-19788) Volume 41, Issue 43, 16 November 2016 , Pages 19781-19788) described the use of a nickel-vanadium catalyst on Al2O3 for steam reforming of dimethyl ether or methanol. The catalyst was obtained by multi-stage impregnation of a corundum support, in the form of Raschig rings, with nickel and vanadium salts, with the vanadium content ranging from 0.5% to 3% by weight. In turn, the publication Biofuel steam reforming catalyst for fuel cell application (Catalysis Today Volume 254, 1 October 2015, Pages 129-134) describes their use in fuel cells.

The technical problem facing the invention is to provide a heterogeneous nickel-vanadium catalyst for carbon dioxide valorization processes, such as dry reforming or hydrogenation, which would be resistant to carbonization or thermal deactivation, would have constant activity during the entire process and would be characterized by a slight decrease in activity during it, not more than 3%. As a result of carbonization of the catalyst, the conversion rate of the substrates decreases because the active sites are poisoned. Catalysts used in the reforming and valorization processes of carbon dioxide are also subject to thermal deactivation, which leads to the active crystallites forming larger agglomerates, which in turn form even larger agglomerates, resulting in a loss of the number of active sites and a decrease in conversion efficiency. The catalyst should also be stable under the process conditions, have high conversion efficiency and be easy to obtain, without the need to use solutions of reagents harmful to health and the environment. Surprisingly, the above problems were solved by the presented invention.

The first subject of the invention is a nickel-vanadium catalyst on a solid support, characterized in that the weight ratio of nickel to vanadium in the catalyst is from 1 to 25, with the vanadium being deposited on the solid support in the form of nickel oxide crystallites and/or vanadium oxide crystallites and /or crystallites of mixed oxides of nickel and vanadium, the support being obtained from a precursor with a hydrotalcite structure.

In a preferred embodiment of the invention, the weight ratio of nickel to vanadium is from 1.6 to 25.

In yet another preferred embodiment of the invention, the vanadium content is from 0.5% to 5% by weight, and the nickel content is 7% by weight.

In a further preferred embodiment of the invention, the carrier obtained from a precursor with a hydrotalcite structure and the general formula ViNimAln(CO3)x(OH)yzH2O contains vanadium from 0.2% to 0.5% by weight.

In yet another preferred embodiment of the invention, the carrier is in the form of porous balls, the diameter of which is from 4 mm to 6 mm, and their specific surface area is BET 120-130 m ² /g.

In yet another preferred embodiment of the invention, the pore volume of the carrier is up to 0.27 cm ³ /g to 0.36 cm ³ /g, and their size is from 54 A to 102 A.

The second subject of the invention is a method for obtaining a nickel-vanadium catalyst on a solid support, including:

a) obtaining a catalyst precursor,

b) impregnating the precursor with a vanadium salt solution,

c) drying and calcining the impregnated precursor, characterized in that the precursor in step a) is obtained in the co-precipitation reaction of nickel nitrate, ammonium vanadate, sodium aluminate and sodium carbonate, by contacting solutions of nickel nitrate, ammonium vanadate, sodium aluminate and sodium carbonate, and the co-precipitation is carried out at a temperature of 75°C, and the pH during the co-precipitation is from 8.2 to 8.5, the obtained precursor suspension is washed, dried, calcined and granulated, the precursor containing vanadium in amounts from 0.2% to 0.5% by weight, and the precursor obtained in step a) is impregnated with a solution of ammonium vanadate (V) in step b), the weight ratio of nickel to vanadium in the catalyst after impregnation being from 1 to 25.

In a preferred embodiment of the invention, the weight ratio of nickel to vanadium is from 1.6 to 25.

In yet another preferred embodiment of the invention, the vanadium content is from 0.5% to 5% by weight, and the nickel content is 7% by weight.

In a preferred embodiment of the invention, the concentration of nickel nitrate corresponds to a nickel concentration of 120 g Ni/dm ³ .

In another preferred embodiment of the invention, the suspension is washed so that the conductivity of the leachate is not higher than 300 μβ.

In yet another preferred embodiment of the invention, the concentration of ammonium vanadate (V) corresponds to a vanadium concentration of 10 g V/dm ³ .

In another preferred embodiment of the invention, the precursor is calcined for 4 hours and at a temperature of 450°C.

In another preferred embodiment of the invention, the impregnated precursor is dried at 120°C for 12 hours.

In yet another preferred embodiment of the invention, the impregnated precursor is calcined for 3 hours and at a temperature of 500°C.

In another preferred embodiment of the invention, impregnation is carried out with a solution of ammonium vanadate (V) with a concentration of 1.93*10'4 mol/dm ³ to 9.63*10'5 mol/dm ³ .

Another subject of the invention is the use of a nickel-vanadium catalyst on a solid support in carbon dioxide valorization processes.

In a preferred embodiment of the invention, carbon dioxide valorization processes are selected from the group consisting of: dry reforming reaction or hydrogenation reaction.

In another preferred embodiment of the invention, substrates selected from the group consisting of: hydrocarbons with a carbon chain length of 1 to 4 carbon atoms, hydrocarbons with a carbon chain length of 1 to 4 carbon atoms containing atoms other than a carbon atom selected from the group including atoms: O, Cl, S.

In yet another preferred embodiment of the invention, carbon dioxide valorization processes involve substrates selected from the group consisting of: aliphatic ethers with a carbon chain length of 1 to 4 carbon atoms, aliphatic hydrocarbons with a carbon chain length of 1 to 4 carbon atoms.

Nickel-vanadium catalysts according to the invention were obtained in a two-stage way: i.e. (1) co-precipitation of a precursor with a dominant hydrotalcite structure and the general formula: ViNimAln(CO3)x(OH)yzH2O with a vanadium content in the range of 0.2-0.5% resulting from EDX tests and lack of sample homogeneity and (2) to impregnate with NH4VO3 solution so as to obtain at most 5% of vanadium in the form of V2O5. They are more resistant to soot formation. Typically for hydrotalcite, the stoichiometric formula can be written as Mg6Al2(OH)i6CO3x4H2O. However, the value of the molar ratio of metal cations is in the range of 0.15-0.34. In the case of the solution according to the invention, when the vanadium content is 0.5-5%, the formula could theoretically look as follows: ViNimAln(CO3)x(OH)yzH2O, where in fact we obtain from the synthesis a maximum vanadium content of 0.5%, conditioned by the value of the molar ratio of metal cations for hydrotalcite natural. Why is it necessary to introduce more vanadium using the impregnation method? However, the ratio of vanadium and nickel (III) ions to aluminum and nickel (II) ions is still in the range of 2-3, which guarantees the formation of a layer structure with a brucite structure. Compared to catalysts based only on nickel, they have more than twice as much activity. They do not contain active metal centers other than nickel and vanadium, so both they and the method of preparation are simpler, more economical and limit the use of solutions harmful to health and the environment, and do not require the preparation of complexes with EDTA during the synthesis of the catalyst. It was also found that, as a result of the interactions of individual catalyst components, Ni-V systems constitute an active material resistant to carbonization and soot formation. Although charring occurs, it is eliminated immediately by vanadium, which is known as a very good oxidation catalyst. The resulting soot is oxidized to CO or CO2, and vanadium, in the form of V2O5, acts as an "oxygen storage component". In this cycle, V ⁺⁵ is reduced to V ⁺³ , and oxygen is released for the soot oxidation reaction. Moreover, the catalysts obtained according to the invention do not contain magnesium, and the elimination of Mg affects the rate of the polymerization reaction, i.e. the formation of carbon chains and the formation of coke.

This catalyst was obtained from a hydrotalcite precursor, which provides a number of advantages in the final catalyst, especially (i) large specific surface area, which, taking into account the volume and pore size (0.27-0.36 cm ³ /g and 54-102 A, respectively) ensures a large contact surface with reagents, especially in the gas phase, (ii) a very high degree of dispersion of transition metals in the final catalyst of hydrotalcite origin, which ensures very good contact between the individual phases of the catalyst, (iii) high thermal stability of the catalyst - the precursor is calcined usually at a temperature of 773 -1023K. An additional advantage of catalysts obtained from hydrotalcite precursors is the chemical composition of the catalyst, mainly in the form of mixed post-calcined oxides, and the ease of synthesis, which makes it possible to synthesize materials containing various transition metals in a relatively wide range of their content. Natural hydrotalcite is a mixed layered magnesium-aluminum hydroxide with the formula: Mg6Al2(OH)i6CO3x4H2O. [Cavani F., Trifiro F., Vaccari A.: Hydrotalcite type anion clays: preparation, properties and applications. Catalysis Today 1991,11, 2,173]. In our case, the hydrotalcite structure presented in this way is a model for synthetic materials composed of brucite-like layers with the general formula [M ^ll 1-xM ^ll x(OH)2] ^x+ A ^z- x/z-nH2O, where MII and M ^m are cations divalent and trivalent metals, respectively, and A are interlayer anions; x is the molar ratio of metal cations, the value of which is in the range 0.15-0.34. In natural hydrotalcite, brucite-like layers consist of octahedrally coordinated metal cations MII and M ^m through hydroxyl groups, and part of the Mg ²⁺ cations is replaced by Al ³⁺ cations. The positive charge of brucite-like layers is compensated by anions, which, together with water molecules, are located in the interlayer spaces. In synthetic hydrotalcite materials, some of the Mg ²⁺ and/or Al ³⁺ ions are substituted with other di- or trivalent cations of similar sizes. And the most common cations in the MII and μ ¹¹¹ positions are: MII - Mg ²⁺ , Cu ²⁺ , Co ²⁺ , Ni ²⁺ , Zn ²⁺ and Fe ²⁺ , and M ^m Al ³⁺ , Cr ³⁺ , Fe ³⁺ . As a result of calcination of hydrotalcite materials at temperatures of 773-1023 K, mixed metal oxides and spinel phases are obtained. An oxide is understood as an oxide containing cations of more than one element or cations from one element in several oxidation states [Kooli K., Riverso V., Uliborri MA: Preparation and Study of Decavanadate-Pillared Hydrotalcite-like Anion Clays Containing Transition Metal Cations in the Layers. 1. Samples Containing Nickel-Aluminum Prepared by Anionic Exchange and Reconstruction. Inorganic Chemistry 1995, 34, 21, 5114].

In the presented invention, the MII and MIII positions are filled with the following cations, respectively: MII Ni ²⁺ , V ²⁺ and M ^IH - Al ³⁺ , V ³⁺ . As a result of calcination of hydrotalcite materials at temperatures of 773-1023 K, mainly mixed metal oxides are obtained, because the calcination temperature is approximately 773 K lower than that required to create a spinel phase, e.g. NiAbO4. Mixed oxides observed in XRD indicate possible phases: NiO, NiO2, ALO3, V2O5, V2O3. Taking into account the calcination conditions, it is also possible to produce V2O3 oxides (JCPDF #85-1411) or non-stoichiometric NixV2Os oxides, or mixed oxides of the Ni-V2O5 type, where the Ni/V ratio does not exceed 0.08.

The developed catalysts are characterized by durability, operational stability and ease of production. These catalysts can operate as a fixed, single bed, or as a sandwich bed, consisting of several layers of different catalysts. Compared to traditional reactions, the catalysts prepared in this way have 2-3 times greater catalytic activity in reforming and hydrogenation reactions, which means that they may be important for fixed-bed reformers for the conversion of hydrocarbons to syngas or direct hydrogenation of carbon dioxide to C1-C3 hydrocarbons.

Examples of implementation of the invention will be illustrated in the drawing, where the figures show: Fig. Photos from a transmission electron microscope: A) Ni/NiOx-Al2O3, B) Ni-0.5V2O5/VxOyNiOx-AI2O3, C) Ni-1V2O5/VxOy-NiOx- AI2O3, D) Ni-3V2O5/VxOy-NiOx-Al2O3, E) Ni-5V2O5/VxOy-NOx-AI2O3, E) 3V2O5/VxOy-AI2O3; Fig. 2 EDX analysis of the composition of the Ni/NiOx-ALO3 nickel catalyst; Fig. 3 EDX analysis of the composition of the Ni-0.5V2O5/VxOy-NiOx-Al2O3 catalyst; fig. 4 fig. 3 EDX analysis of the composition of the Ni-1V2O5/VxOy-NiOx-AI2O3 catalyst; fig. 5 EDX analysis of the composition of the Ni-3V2O5/VxOy-NiOx-AbO3 catalyst; Fig. 6 EDX analysis of the composition of the Ni-5V2O5/VxOy-NiOx-AbO3 catalyst; Fig. 7 EDX analysis of the composition of the 3V2O5/VxOy-Al2O3 catalyst; Fig. 8 XRD characteristics of the catalysts: A) 3V2O5/VxOy-AŁO3, B) Ni/NiOx-Al2O3, C) Ni-0.5V2O5/VxOy-NiOx-AI2O3, D) Ni-1V2O5/VxOy-NiOx-AI2O3, E) Ni-3V2O5/VxOy-NiOx-AI2O3,

F) Ni-5V2O5/VxOy-NiOx-Al2O3; Fig. 9 XPS characteristics of the catalysts in the Ni2p area: a) Ni/NiOxAl2O3, b) Ni-0.5V/VxOy-NiOx-AI2O3, c) Ni-1V2O5/VxOy-NiOx-AbO3, d) Ni-3V2O5/VxOy-NiOx -Al2O3, e) Ni-5V2O5/VxOy-NiOx-Al2O3; Fig. 10 XPS characteristics of the catalysts in the O1s and V2p area a) Ni/NiOx-Al2O3, b) Ni-0.5V2O5/VxOy-NiOx-AI2O3, c) Ni-1V2O5/VxOy-NiOx-Al2O3, d) Ni-3V2O5/ VxOy-NiOxAI2O3, e) Ni-5V2O5/VxOy-NiOx-AI2O3; Fig. 11 change of the conversion rate over time for A) Ni/NiOx-Al2O3, B) 3V2O5/VxOy-AI2O3, C) Ni-0.5V2O5/VxOy-NiOx-Al2O3, D) Ni-1V2O5/VxOy-NiOx-AI2O3, E) Ni-3V2O5/VxOyNiOx-AI2O3, F) Ni-5V2O5/VxOy-NiOx-Al203 for the dry reforming reaction at 723 K; Fig. 12: change of the conversion rate over time for A) Ni/NiOx-ALO3, B) 3V2O5/VxOy-AbO3, C) Ni-0.5V2O5/VxOy-NiOx-AI2O3, D) Ni-1V2O5/VxOy-NiOx-AI2O3, E) Ni-3V2O5/VxOy-NiOx-AI2O3, F) Ni-5V2O5/VxOy-NiOx-AI2O3 for the CO2 hydrogenation reaction at 573 K, Fig. 13 Ni/NiOx-Al2O3 catalyst, which is a mixture of nickel-aluminum oxides from the precursor with a dominant hydrotalcite structure and the general precursor formula Ni _m Aln(CO3)x(OH)yzH2O; Fig. 14: change of selectivity to methane with temperature for the CO2 hydrogenation reaction on the catalyst A) Ni/NiOx-Al2O3, B) 3V2O5/VxOy-AbO3, C) Ni^OsMcOy-NiO^AhOe; Fig. 15 of the BET isotherm for: A) Ni/NiOr-AbOe, B) Ni-0.5V2O5/VxOy-NiOx-AbO3, C) Ni-1V2O5/VxOy-NiOxAI2O3, D) Ni-3V2O5/VxOy-NiOx-AI2O3, E) Ni-5V2O5/VxOy-NiOx-AI2O3, F) 3V2O5/VxOy-AI2O3.

Example 1 Nickel-vanadium catalyst

Physicochemical characterization of nickel-vanadium catalyst samples (Table 1) using XRD (Figure 4b-4e) revealed the existence of two different phases for nickel-vanadium catalysts, i.e.: one phase corresponding to a-AbO3 (JCPDS 42-1468 JCPDS) and traces of the phase a-AbO3 (jCpdS 75-0921). The second phase is associated with the presence of NiAbO4 (JCPDS 01-1299). Nickel was identified as NiO2 (JCPDS 03-065-6920) and NiO2 (JCPDS 98-007-8698). Signals from metallic nickel and vanadium were not identified using XRD, which is most likely due to their rather small amount and/or the signals from other catalyst components overlapped with the signals from the above-mentioned components. structures.

The results of XPS measurements (Figure 9 and Figure 10) indicated the presence of all components, i.e. nickel and vanadium, in the modified catalyst. Figure 8 shows the deconvolution of the peaks for the Ni 2p3/2 and V 2p regions. Analysis of the XPS measurement results showed the presence of signals for surface Ni ²⁺ sites originating from NiO (position 855.1-855.6 eV) and Ni ²⁺ originating from NiAl2O4 (position 856.0-856.9 eV) for all nickel-vanadium catalysts. In the case of samples containing vanadium, the number of oxide/spinel surface sites varies depending on the chemical composition of the sample. For the obtained catalysts, regardless of the vanadium content, the peak around 856.9 eV is more pronounced. As the concentration of vanadium in the sample increases, this peak broadens and is shifted towards higher bond energies (BE), by approximately 0.2 eV, and the peak from NiO is more dominant.

For catalysts containing vanadium, an additional signal of ~852.9 eV is observed, which is most likely related to the presence of surface NiO sites. This signal becomes more pronounced as the vanadium content in the sample increases. This effect may be related to the vanadium-nickel interaction and the increase in the reducibility of the catalyst sample.

In a nickel-vanadium catalyst, the vanadium oxide is not in the form of a film, but in the form of dispersed nanoparticles or mixed nickel-vanadium nanoparticles on the surface of the oxide support. It results from the stoichiometry of the catalyst composition, which gives an average of 0.5 to 4.9 vanadium atoms per m ² (from BET measurements).

BET measurements (Fig. 15) were carried out in the ASAP2020 V4.03(V4.03 H) apparatus (nitrogen adsorption and desorption according to the procedure according to Silica-Alumina iso at a temperature of 77-78K). The results showed that the specific surface area is BET 120-130 m ² /g, and the pore volume and size are 0.27-0.36 cm ³ /g and 54-102 A, respectively. Both the nickel catalyst (Ni/NiOx-AbO3) and the nickel- vanadium (Ni-xV2O5/VxOy-NiOx-AbO3 x=0-5%) have the form of balls with a diameter of 4 mm to 6 mm. Well-developed specific surface area and pore volume and size of 0.27-0.36 cm ³ /g and 54-102 A, respectively, ensure a large contact surface with the reactants, especially in the gas phase, and a very high degree of dispersion of transition metals in the final catalyst of hydrotalcite origin, which ensures very good contact between the individual phases of the catalyst.

Fine crystallites are visible only on XRD at concentrations above 3% as the V2O5 phase. XPS measurements show that vanadium affects the oxidation state of nickel, i.e. the more vanadium, the more nickel in the form of NiO. Therefore, based on the XPS measurements, it can be concluded that the vanadium nanoparticles/nanocrystallites must be relatively close to/in contact with the nickel nanoparticles. This is also evidenced by the fact that the activity increases even with a small amount of vanadium and vanadium plays a protective role in maintaining the activity of nickel for as long as possible. Moreover, XPS tests have shown that for nickel-vanadium catalysts, vanadium occurs in +3, +4 and +5 oxidation states. Therefore, V2O3 and V2O5 oxides are possible (Fig. 10). XRD studies identified mainly V2O5, because the bands characteristic of V2O3, V2O5 and those coming from nickel oxides overlap in the same 2θ region.

TEM images (Figure 1A) Ni/NiOx-AbO3, B) Ni-0.5V2O5/VxOy-NiOx-AbO3, C) Ni-1V2O5/VxOy-NiOxAI2O3, D) Ni-3V2O5/VxOy-NiOx-AI2O3, E) Ni -5V2O5/VxOy-NiOx-AbO3, F) 3V2O5/VxOy-AI2O3) show the existence of nanoparticles, but it is difficult to distinguish nanoparticles of Ni-NiO-NiO2 and vanadium oxide and phases

PL 244205 Β1 mixed oxides. EDX analysis from a given area shows the presence of both nickel and vanadium, so we can assume that these nanoparticles are at least in close contact with each other. Transmission electron microscope photos were obtained using a transmission electron microscope model Philips CM200 (200 kV) equipped with an EDX (Energy Dispersive X-ray) detector, table 3. The sample in powder form was placed on a copper mesh covered with a layer of carbon. It was not possible to measure the sizes of V ₂ Os crystallites using the above methods due to their content being too small and the bands too weak compared to nickel (XRD measurements) and too low contrast (TEM measurements). The presence and form of vanadium were determined based on XPS measurements.

Table 1 Catalysts obtained according to the invention and comparative catalysts.

Name Ni (% wt) V (% wt) Ni/NiO _x -Al2O3 (comparative example) 7 0 Ni-0.5V ₂ O ₅ /V _x O _y -NiO _x -AI ₂ O ₃ 7 0.5 Ni-lV ₂ O ₅ /V _x O _y -NiO _x -AI ₂ O ₃ 7 1 Ni-3V ₂ O ₅ /V _x O _y -NiO _x -Al ₂ O ₃ 7 3 Νί-5ν ₂ Ο ₅ /ν _χ Ο _ν -ΝϊΟ _χ -ΑΙ ₂ Ο ₃ 7 5 3V ₂ O ₅ /V _x O _y -Al ₂ O ₃ (comparative example) 0 3

Table 2 Crystallite sizes of nickel-vanadium catalysts determined on the basis of XRD and TEM measurements.

Crystallite size Ni/NiO _x A1 ₂ O ₃ Ni-0.5V ₂ O ₅ /V _x O _y NiO _x -AI ₂ O ₃ Ni-lV ₂ O ₅ /V _x O _y NiO _x -AI ₂ O ₃ Ni-3V ₂ O ₅ /V _x O _y - NiO _x -AI ₂ O ₃ Ni-5V ₂ O ₅ / V _x O _y -NiO _x ai ₂ o ₃ DpNi(nm)™ <18 <17 <14 <15 <10 DpNi(nm)™ <13 <13 <13 <11 <7

Table 3 Weight content of Wt (in percent) and atomic A (in percent) for individual elements determined by the EDX method

Tue% At% APPROX Al K Ca K V K Ni K SUM APPROX Al K Ca K V K Ni K SUM Ni/NiO _x ΑΙ ₂ Ο ₃ (comparative example) 61.52 37.28 0.78 0.00 0.42 100 72.62 26/62 0.37 0.00 0.39 100 Ni- 0.5V ₂ O _s /V _x O _v NiO _x -AI ₂ O ₃ 59.5 38.67 0.86 0.08 0.89 100 71.65 27/61 0.41 0.03 0.29 100 Ni-lV ₂ O ₅ /V _x O _y - NiO _x -AI ₂ O ₃ 62.85 36.50 0.31 0.04 0.29 100 74.19 25.55 0.15 0.02 0.09 100 Ni-3V ₂ O ₅ /V _x O _y - NiO _x -Al ₂ O ₃ 57.15 41.46 1/02 0.08 0.30 100 69.48 29/89 0.49 0.03 0.10 100 Ni-5V ₂ O ₅ /V _x O _¥ - NiO _x -AI ₂ O ₃ 52.28 46.89 0.18 0.07 0.58 100 65/08 34.61 0.09 0.03 0.20 100 3V ₂ O ₅ /V _X O _¥ - AI ₂ O ₃ (comparative example) 56.17 43.54 0.19 0.08 0.02 100 68.29 31.58 0.09 0.03 0.01 100

Example 2 Method of obtaining nickel and nickel-vanadium catalysts.

Reagents and materials

Hydrated nickel(II) nitrate Ni(NO3)2-6H2O, sodium hydroxide (NaOH), sodium aluminate (NaAIO2), sodium carbonate Na2CO3 and ammonium vanadate (NH4VO3).

2a) Ni/NiOx-Al2O3 system

The Ni/NiOx-Al2O3 system, which is a mixture of basic nickel-aluminum carbonates with a dominant hydrotalcite structure with the general formula: NimAln(CO3)x(OH)yzH2O, was obtained by co-precipitation. Co-precipitation was carried out by simultaneous dosing of a nickel nitrate solution with a concentration of 120 g Ni/dm ³ and an alkaline solution of sodium aluminate and sodium carbonate into a thermostated (75±5°C) HWS reactor with a capacity of 5 dm ³ , maintaining the pH of the resulting suspension in the range of 8.2-8.5 . The obtained precursor was washed from undesirable substances (leachate conductivity below 300 μS) using a filtration unit from HWS. Then the material was dried at 110°C for 12 h and calcined at 450°C for 4 h.

After calcination, the mass was granulated on a granulation plate using demineralized water into balls with a diameter of 4-6 mm. The Ni/NiOx-AbO3 system was then dried at 120°C for 12 h and calcined at 500°C for 3 h.

The Ni/NiOx-Al2O3 system is also a carrier of a nickel-vanadium catalyst and can be used as a catalyst in carbon dioxide valorization reactions. This carrier contains Ni. After calcination, the precursor decomposes and nickel-aluminum mixed oxides are formed.

Ni/NiOx-Al2O3 system; as a reference catalyst, it contains 7% by weight of nickel in the form of NiO0x-AbO3 mixed oxide. This is a huge advantage because the incorporation of nickel into the hydrotalcite structure and then obtaining a mixed oxide structure from it prevents the formation of a nickel-aluminum spinel structure, which causes a decrease in catalytic activity in the case of catalysts obtained by impregnation as in the case of solutions described in the prior art.

2b) Ni-0.5V2O5/VxOy-NiOx-AI2O3 system

Nickel-vanadium catalysts were obtained in a two-step process. First, by co-precipitation, a precursor was obtained, which was a mixture of basic vanadium-nickel-aluminum carbonates with a dominant hydrotalcite structure with the general formula: ViNimAln(CO3)x(OH)yzH2O, where the amount of vanadium did not exceed the value determined by the ion molar ratio of 0.15-0.34. Co-precipitation was carried out by simultaneous dosing of an alkaline solution of sodium aluminate and sodium carbonate and a nickel nitrate solution with a concentration of 120 g Ni/dm ³ into a thermostated (75±5°C) HWS reactor with a capacity of 5 dm ³ , maintaining the pH of the resulting suspension in the range of 8.2- 8.5. At the same time, a solution of ammonium vanadate (V) with a concentration of 10 g V/dm ³ was added. The obtained precursor was washed from undesirable substances (leachate conductivity below 300 μS) using a filtration unit from HWS. Then the material was dried at 110°C for 12 h and calcined at 450 C for 4 h.

After calcination, the mass was granulated on a granulation plate using demineralized water into balls with a diameter of 4-6 mm. The Ni-0.5V/VxOy-NiOx-Al2O3 system was then dried at 120°C for 12 h and calcined at 500°C for 3 h.

The formed carrier balls were impregnated with a NH4VO3 solution with a concentration of 1.93*10-4 mol/dm ³ , respectively, to obtain 0.5% by weight in the final catalyst. vanadium. Then it was dried at 120°C for 12 h and calcined at 500°C for 3 h.

2c) Ni-1V2O5/VxOy-NiOx-AI2O3 system

The Ni-1V/NiOx-Al2O3 system was obtained similarly to the precursor as in point 2b), which was then impregnated with a NH4VO3 solution with a concentration of 6.10*10-4 mol/dm ³ , respectively, to obtain 1% by weight in the final catalyst. vanadium. It was dried at 120°C for 12 h and calcined at 500°C for 3 h.

2d) Ni-3V2O5/VxOy-NiOx-AI2O3 system

The Ni-3V/VxOy-NiOx-Al2O3 system was obtained similarly to the one from the precursor as in point 2b), which was then impregnated with a NH4VO3 solution with a concentration of 9.63*10-4 mol/, respectively, to obtain 3% by weight in the final catalyst. vanadium. It was dried at 120°C for 12 h and calcined at 500°C for 3 h.

2e) Ni-5V2O5/VxOy-NiOx-Al2O3 system

The Ni-5V/NiOx-Al2O3 system was obtained similarly to the precursor as in point 2b), which was then impregnated with a NHWO3 solution with a concentration of 9.63*10 ^-5 mol/dm ³ mol/, respectively, to obtain 5% by weight in the final catalyst. vanadium. It was dried at 120°C for 12 h and calcined at 500°C for 3 h.

Physicochemical characterization of catalyst samples using XRD (Fig. 8, lines A-F) revealed the existence of two different solid phases for nickel catalysts (Fig. 8, line B), containing no vanadium and constituting reference catalysts in relation to the nickel-vanadium catalyst, i.e.: one phase corresponding to a-AbO3 (JCPDS 42-1468 JCPDS) and trace amounts of the y-AbO3 phase (JCPDS 75-0921). The second phase is associated with the presence of NiAbO4 (JCPDS 01-1299). Nickel was identified as NiO (JCPDS 03-065-6920) and NiO2 (JCPDS 98-007-8698). Signals from metallic nickel and vanadium were not identified using XRD, which is most likely due to their rather small amount and/or the signals from other catalyst components overlapped with the signals from the above-mentioned components. structures.

The partial formation of mixed oxides or their crystallites in very close contact with each other can be concluded based on chemical shifts from XPS measurements, since different spectral profiles are visible when increasing amounts of vanadium are introduced. This proves that the presence of vanadium affects nickel and the proportion of peaks 856.9 / 855.2 decreases with the increase in the amount of vanadium (the peak with a maximum of 855.2 increases with the increase in the amount of vanadium, Fig. 9).

The results of XPS measurements indicated the presence of all components, i.e. nickel and vanadium, in the modified catalyst. Figure 2 shows the peak deconvolution for the Ni2p3/2 region. Analysis of the XPS measurement results showed the presence of signals for surface Ni ²⁺ sites originating from NiO (position 855.1-855.6 eV) and Ni ²⁺ originating from NiAbO4 (position 856.0-856.9 eV). Deconvolution of the peak for the V 2p and O 1s region according to Figure 10 indicated the presence of signals for the surface V ³⁺ , V ⁴⁺ and V ⁵⁺ sites originating from V2O3 (position 515.1-516.6 eV) and V2O5 (position 516.3-517.5 eV) , Fig. 10.

Example 3 Method of obtaining a vanadium-aluminum catalyst (3V2O/VxOyAl2O3 system, comparative example).

Reagents and materials

Sodium hydroxide (NaOH), sodium aluminate (NaAIO2) and sodium carbonate Na2CO3, ammonium vanadate NH4VO3.

First, by co-precipitation, a precursor was obtained which was a mixture of basic vanadium-aluminum carbonates with a dominant hydrotalcite structure with the general formula: VmAln(CO3)x(OH)yzH2O, where the amount of vanadium did not exceed the value determined by the ion molar ratio of 0.15-0.34. Co-precipitation was carried out by simultaneous dosing of an alkaline solution of sodium aluminate and sodium carbonate into a thermostated (75±5°C) HWS reactor with a capacity of 5 dm ³ , maintaining the pH of the resulting suspension in the range of 8.2-8.5. The obtained precursor was washed from undesirable substances (leachate conductivity below 300 μS) using a filtration unit from HWS. Then the material was dried at 110°C for 12 h and calcined at 450°C for 4 h. After calcination, the mass was granulated on a granulation plate using demineralized water into balls with a diameter of 4-6 mm. The formed balls were impregnated with a NH4VO3 solution with a concentration of 6*10 ^-4 mol V/dm ³ selected so as to obtain 3% by weight in the final catalyst. vanadium. The V2O5/VxOy-Al2O3 systems were then dried at 120°C for 12 h and calcined at 500°C for 3 h.

Example 4 Use of a nickel-vanadium catalyst (Ni-zV2O5/VxOy-NiOx-Al2O3, where vanadium content = 0-5% by weight) in carbon dioxide valorization processes

A study of catalytic activity and selectivity for the CO2 reforming and CO2 hydrogenation processes was carried out for nickel-vanadium catalysts according to the invention, presented in Table 1.

To determine the optimal conditions for the catalytic reforming process, the influence of the reaction temperature (25-500°C) was examined and a reactant ratio of 1 for the inlet gases (reforming reaction) and 10-30% hydrogen concentration for the hydrogenation process were taken into account.

Catalysts according to the invention are used in valorization reactions of substrates, which may be aliphatic hydrocarbons, aliphatic alcohols, aliphatic ethers or aliphatic acids. It is also possible to use it on substrates containing heteroatoms such as chlorine or sulfur. It is particularly advantageous to use them in reactions where the reagents are aliphatic ethers with a chain length of 1 to 4 carbon atoms or aliphatic hydrocarbons with a chain length of 1 to 4 carbon atoms. The catalysts according to the invention are used for both straight- and branched-chain substrates. However, this does not exclude the use of reagents such as aliphatic acids containing from 1 to 4 carbon atoms, such as acetic acid or formic acid, or aliphatic alcohols with a chain length of 1 to 4 carbon atoms.

a) in the reforming reaction, based on the example of the dry reforming reaction of dimethyl ether (DME)

According to Antoninho Valentini et al. (Applied Catalysis A: General 255 (2003) 211-220), the results obtained for similar systems synthesized using organic reagents such as ethylene glycol, ethanol, citric acid, showed that the amount of soot deposited (Coke deposition gc /gcat) did not depend on the amount of vanadium introduced (0.8-3.7) for catalysts containing 10% Ni (wt%) and increased significantly (by 6000%) for the most stable system, i.e. 22 Ni and 8.5 V wt%, according to the publication cited above .

The Ni-3V2O5/VxOy-NiOx-Al2O3 catalyst obtained according to the invention showed: the amount of accumulated soot at the level of 0.003-0.005 gc/gcat (gram of carbon per gram of catalyst) and a stable activity of 75% for the entire duration of the test, i.e. a minimum of 27 hours . At this time, the H2/CO ratio was 0.93 for the reaction described by the equation CH3-O-CH3+CO2=3CO+3H2. Throughout the entire experiment, the reaction on the nickel-vanadium catalyst proceeds almost stoichiometrically. For ideal conditions, taking into account the conversion reactions of carbon monoxide with water vapor, CO conversion (Reverse Water Gas Shift reaction RWGS), the ratio of the resulting H2/CO products should be 1 according to the equation CH4 + CO2 = 2CO + 2H2.

The dry reforming test was carried out at various temperatures, from 25 to 500°C, in a quartz tubular reactor (outer diameter = 10 mm). 50 mg of sample was loaded into the reactor and subjected to He flow while heating to 500°C. The reactors were then cooled and dimethyl ether was introduced into the reactor. Then the reactor was heated to 500°C with a temperature increase of 10°C min ^-1 . Gas mixtures were prepared from gases in cylinders and controlled using mass flow controllers (Bronkhorst). Dry reforming reactions were carried out for a DME/CO2 gas mixture with a ratio of (3-1:1, preferably 1:1). A Hiden QGA mass spectrometer (MS) was used to control the product distribution at the reactor outlet. The total gas flow rate was 50-100 ml min ^-1 (GHSV = 2.1-4.5 10 ³ h ^-1 , at 1 atm and 293 K). Temperature-programmed reactions (i) desorption (TPD, in He), (ii) oxidation (TPO, in 5% O2 in He) and (iii) reduction (TPR, in 5% H2 in He) were performed to 1) determine the reducibility catalyst and 2) calculation of the carbon balance, which was 5% for the Ni/NiO-AbO3 nickel catalyst and below 3% for the nickel-vanadium catalysts, respectively Ni-0.5V2O5/VxOy-NiOx-Al2O3 2.7%, Ni-1V2O5/VxOy- NiOx-Al2O3 2.6%, Ni-3V2O5/VxOy-NiOx-AI2O3 2.1% Ni-5V2O5/VxOy-NiOx-Al2O3 2.1%. Temperature-programmed reduction tests showed that the addition of vanadium shifts nickel oxidation towards higher temperatures by approximately 30°C, compared to the catalyst without vanadium.

b) in the CO2 hydrogenation reaction

In our case, the developed Ni-3V2O5/VxOy-NiOx-Al2O3 catalyst shows an activity of 96% at a temperature of 280°C. At this temperature, carbon dioxide conversions of 20% were achieved for catalysts based on noble metals. Catalysts with a lower content of vanadium show stable, but lower activity by approximately 5-15% compared to the catalytic system containing 3% by. vanadium (Figure 12). A higher vanadium content does not significantly improve the activity or selectivity of the catalyst.

This is the thermodynamic region of the reaction, so the yield to methane and selectivity is 98%.

The hydrogenation test was carried out in the temperature range from 25°C to 500°C in a quartz tubular reactor (outer diameter = 10 mm). 50 mg of the Ni-3V2O5/VxOy-NiOx-Al2O3 catalyst sample was loaded into the reactor and subjected to He flow while heating to 500°C. Then the reactor was heated to 500°C with a temperature increase of 10°Cmin ^-1 . Gas mixtures were prepared from gases in cylinders and controlled using mass flow controllers (Bronkhorst). Hydrogenation was carried out for a H2/CO2 gas mixture with a ratio of (30-15:1, preferably 30:1). A Hiden QGA mass spectrometer (MS) was used to control the product distribution at the reactor outlet. The total gas flow rate was 50-100 ml min- ¹ (GHSV = 2.1-4.5 10 ³ O-AbO3, Ni-0.5V2O5/VxOy-NiOx-AI2O3, Ni-1V2O5/VxOy-NiOx-AI2O3, Ni -3V2O5/VxOy-NiOx-AI2O3, Ni-5VO5/VOy-NiOx-AI2O3 and the results of the conversion change over time are shown in Fig. 12. Temperature-programmed oxidation reactions (TPO, in 5% O2 in He) were carried out for the catalyst samples after the reaction in order to calculate the carbon balance, which was 5% for the nickel catalyst and below 2% for the nickel-vanadium catalysts, i.e. Ni-0.5V2O5/VxOy-NiOx-Al2O3 1.9%; Ni-1V2O5/VxOy-NiOx-Al2O3, respectively 1.7%, Ni-3V2O5/VxOyNiOx-Al2O3l,4% Ni-5V2O5/VxOy-NiOx-Al2O3 1.3%.

The developed catalysts are characterized by durability, operational stability and ease of production. These catalysts can operate as a fixed, single bed, or as a sandwich bed, consisting of several layers of different catalysts. This type of bed can be used in reformers intended for reforming also second-generation biofuels, i.e. alcohols, ethers (obtained by dehydration of alcohols, but containing impurities, e.g. chlorine or sulfur, which would need to be oxidized first. Then the first catalytic layer of such a sandwich system would be the richest layer in vanadium, while the subsequent ones have correspondingly less vanadium. For the reforming of more demanding hydrocarbons, where the activation energy of the C-H bond is high, e.g. methane, the first layer could be a system containing a noble metal, while the remaining layers could be made of nickel-vanadium systems according to the invention, which would reduce significantly the cost of the reformer.

Compared to traditional reactions, the catalysts obtained according to the invention show 2-3 times greater catalytic activity in the reforming and hydrogenation reaction (Fig. 11 and 12), which means that they may be important for fixed-bed reformers for the conversion of hydrocarbons to syngas or direct hydrogenation of dioxide carbon to C1-C4 hydrocarbons. It was also found that, as a result of the interactions of individual catalyst components, Ni-V systems constitute an active material, resistant to carbonization and soot formation, as evidenced by stable activity during hydrogenation reactions (Fig. 12) and dry reforming (Fig. 11). , where the decline in activity over 27 hours is 1-1.7%.

Catalysts obtained by co-precipitation according to the invention show a slight decrease in activity in the first 5 hours of the test by approximately 3% and stable activity throughout the entire test period of more than 25 hours. A decrease below approximately 3% is typical for nickel-vanadium catalysts. applied to both processes, i.e. the hydrogenation process (Fig. 12) and dry reforming (Fig. 11), where stable conversion is observed for over 27 h. In the same figures, a very similar course of the curves can be observed for catalysts containing vanadium 0.5% and 1%.

Example 5 Use of a nickel-aluminum catalyst (Ni/NiOx-Al2O3) and in carbon dioxide valorization processes (comparative example)

A study of catalytic activity and selectivity was carried out for the CO2 reforming and CO2 hydrogenation processes for nickel catalysts, i.e. those containing no vanadium. To determine the optimal conditions for the catalytic reforming process, the influence of the reaction temperature (25-500°C) was examined and a reactant ratio of 1 for the inlet gases (reforming reaction) and 10-30% hydrogen concentration for the hydrogenation process were taken into account.

It is known from the literature that carbonization on nickel catalysts causes the separation of nickel from the catalyst mass and such a nickel cluster/nanoparticle ceases to be active (e.g. Garcia-Dieguez, M. Improved Pt-Ni nanocatalysts for dry reforming of methane, Applied Catalysis A: General Volume 377, Issue 1-2, 2010, Pages 191-199;Garcia-Dieguez, M. Nanostructured Pt-and Ni-based catalysts for CO2 - reforming of methane, Journal of Catalysis Volume 270, Issue 1, 2010, Pages 136- 145). In our system, such deactivation is also visible for the Ni/NiOx-Al2O3 catalyst sample (Fig. 11, line A). At the beginning of the reaction, the activity measured by the degree of conversion is over 60%, however, in the first 5 hours it drops by over 20% and after 25 hours of the reaction it is 50% lower than for the Ni-3V/VxOy-NiOx-AbO3 catalyst. Even a small addition of vanadium in the amount of 0.5% makes this activity stable throughout the reaction period and after 25 hours the conversion is still measured at 60% (Fig. 11, line C). An increase in the amount of vanadium in the sample by 3 to 5% (lines E and F, Fig. 11) has a positive effect on the degree of conversion and causes its increase by 40-50% compared to the Ni/NiOx-Al2O3 sample

Example 6 Use of a vanadium-aluminum catalyst (3V2O5/VxOy-AkO3) and in carbon dioxide valorization processes (comparative example)

Figure 12, line A, shows the change in the conversion rate over time for the Ni/NiOx-Al2O3 catalyst sample. At the beginning of the reaction, the activity measured by the degree of conversion is in the range of 37-40%, however, in the first 5 hours it drops by over 45% and after 25 hours of the reaction it is 50% lower than that measured at the beginning of the reaction. The 3V2O5/VxOy-ALO3 vanadium catalyst has an activity of almost 100%, which is stable throughout the entire reaction period (Fig. 12, line B). After 25 hours, the conversion is still measured at 90% (Fig. 12, line B). However, despite 100% conversion, the selectivity to methane is below 17% in the temperature range of 300-400 K (Fig. 14, line B) and drops to below 1% with an increase in temperature, which is caused by the strong oxidizing properties of vanadium. Above 400 K, the main reaction products are carbon dioxide and carbon monoxide.

For nickel-vanadium catalysts, an increase in activity measured by the degree of conversion is observed (Fig. 12, lines C, D, E and F). An increase in the amount of vanadium in the sample by 3 to 5% (lines E and F, Fig. 11) has a positive effect on the degree of conversion and causes its increase by 95-97% compared to the Ni/NiOx-Al2O3 sample. The beneficial effect of the vanadium combination was also demonstrated by selectivity measurement, where for the Ni-3V/VxOy-NiOx-Al2O3 catalyst at a temperature of 300-400 K, the selectivity to methane was 60% higher compared to the Ni/NiOx-Al2O3 sample (Fig. 14, line C ) and amounted to 98% at a temperature of 550-600 K.

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Claims (18)

1. Nickel-vanadium catalyst on a solid support, characterized in that the weight ratio of nickel to vanadium in the catalyst is from 1 to 25, wherein the vanadium is deposited on the solid support in the form of nickel oxide crystallites and/or vanadium oxide crystallites and/or crystallites mixed oxides of nickel and vanadium, the carrier being obtained from a precursor with a hydrotalcite structure, and the vanadium content by weight is from 0.5% to 5%, and the nickel content is 7% by weight, and the catalyst does not have a spinel structure. 2. Catalyst according to claim 1, characterized in that the weight ratio of nickel to vanadium is from 1.6 to 25. 3. Catalyst according to claim 1, characterized in that the carrier obtained from a precursor with a hydrotalcite structure and the general formula ViNimAln(CO3)x(OH)yzH2O contains vanadium from 0.2% to 0.5% by weight. 4. Catalyst according to claim 3, characterized in that the carrier is in the form of porous balls, the diameter of which is from 4 mm to 6 mm, and their specific surface area is BET 120-130 m ² /g. 5. Catalyst according to claim 4, characterized in that the pore volume of the carrier is up to 0.27 cm ³ /g to 0.36 cm ³ /g, and their size is from 54 A to 102 A. 6. A method for obtaining a nickel-vanadium catalyst on a solid support, comprising: a) obtaining a catalyst precursor, b) impregnating the precursor with a vanadium salt solution, c) drying and calcining the impregnated precursor, characterized in that the precursor in step a) is obtained in the co-precipitation reaction of nickel nitrate, ammonium vanadate, sodium aluminate and sodium carbonate, by contacting solutions of nickel nitrate, vanadate (V) ammonium, sodium aluminate and sodium carbonate, and the co-precipitation is carried out at a temperature of 75°C, and the pH during the co-precipitation is from 8.2 to 8.5, the obtained precursor suspension is washed, dried, calcined and granulated, the precursor containing vanadium in an amount from 0.2% to 0.5% by weight, and the precursor obtained in step a) is impregnated with a solution of ammonium vanadate (V) in step b), where the weight ratio of nickel to vanadium in the catalyst after impregnation is from 1 to 25 and the calcination process is carried out at from 773°C to 1023°C, with a vanadium content of 0.5% to 5% by weight, and a nickel content of 7% by weight of the catalyst. 7. Method according to claim 6, characterized in that the weight of nickel to vanadium is from 1.6 to 25. 8. Method according to claim 6, characterized in that the concentration of nickel nitrate corresponds to a nickel concentration of 120 g Ni/dm ³ . 9. Method according to stipulation 6, characterized in that the suspension is washed so that the conductivity of the leachate is not higher than 300 μS. 10. Method according to claim 6, characterized in that the concentration of ammonium vanadate (V) corresponds to the vanadium concentration of 10 g V/dm ³ . 11. Method according to stipulation 6, characterized in that the precursor is calcined for 4 h and at a temperature of 450°C. 12. Method according to stipulation 7, characterized in that the impregnated precursor is dried at 120°C for 12 h. 13. Method according to claim from 7 to 14, characterized in that the impregnated precursor is calcined for 3 h and at a temperature of 500°C. 14. Method according to claim 7, characterized in that the impregnation is carried out with a solution of ammonium vanadate (V) with a concentration of up to 1.93*10 ^-4 mol/dm ³ to 9.63*10' ⁵ ' mol/dm ³ . 15. Use of a solid-supported nickel-vanadium catalyst as defined in claim. 1 or obtained according to claim 6, in carbon dioxide valorization processes. 16. Application according to stipulation 15, characterized in that the carbon dioxide valorization processes are selected from the group consisting of: dry reforming reaction or hydrogenation reaction. 17. Application according to claim from 15 to 16, characterized in that the carbon dioxide valorization processes are subjected to substrates selected from the group consisting of: hydrocarbons with a carbon chain length of 1 to 4 carbon atoms, hydrocarbons with a carbon chain length of 1 to 4 carbon atoms containing atoms other than carbon atom selected from the group consisting of atoms: O, Cl, S. 18. Application according to claim from 15 to 17, characterized in that the carbon dioxide valorization processes are subjected to substrates selected from the group including: aliphatic ethers with a carbon chain length of 1 to 4 carbon atoms, aliphatic hydrocarbons with a carbon chain length of 1 to 4 carbon atoms.