Catalyst for hydrogenating CO2 at low reaction temperatures to form methane, comprising ruthenium oxocarbonate as the active phase

Abstract

The present invention relates to a catalyst comprising a ruthenium oxocarbonate, its preparation method, and its use for the hydrogenation of CO2 to form methane at temperatures below 200°C.

Description

Detailed Description of the Invention

[0001] FIELD OF THE INVENTION The present invention relates to transition metal oxide-based catalysts for the hydrogenation of CO to form methane at low temperatures (below 200°C). More specifically, it relates to monoclinic ruthenium oxide catalysts containing carbon in their crystal structure. This phase is believed to be active for the activation of CO at low temperatures, selectively producing methane as the hydrogenation product.

[0002] Background of the Invention The utilization of CO2 has attracted considerable attention as an alternative carbon source to the use of fossil fuels for the synthesis of chemicals and fuels. Among the various catalytic processes, the hydrogenation of CO2 to obtain methane is particularly interesting from the perspective of storing surplus renewable energy in the form of CH4, which can be easily transported with current drive systems. Most of the processes for the hydrogenation of CO2 to obtain methane are thermal processes, which, unlike electrocatalytic and photocatalytic processes, are much more efficient. Catalysts proposed in the literature for producing CH4 from CO2 are based on metals such as Ni, Ru, Pd, and Rh, either mono- or multimetallic, supported on various metal oxides (TiO2, SiO2, Al2O3, CeO2, ZrO2) or carbon materials (N-doped CNTs), with or without promoters (Na, K, Cs, rare earth elements, etc.) (CN108686635A; CN109433199A; CN108927194A; US3884838A). These catalysts are suitable for high reaction temperatures (250–450 °C), low space velocities (600 h -1 ) and usually operates under excess hydrogen (H2 / CO2 = 11 to 5), improving methane yield. For example, Patent Document CN1107078A describes the use of Ni 0 (2-40%), Ru 0A catalyst composed of sepiolite (60-98%) and sepiolite (0.1-7 wt%) is described. This catalyst is preactivated in H2 at 400 °C for 1 h, and the reaction temperature is 400-450 °C, the space velocity is 6000-9000 h -1 , operating at atmospheric pressure and a H2 / CO2 molar ratio of 4, 58 mol L -1 h -1 Patent document JP01261202 describes a metal phase ruthenium catalyst on an alumina carrier, which can be used at 300-400°C and low space velocity (670 h -1 ) and a pressure of 0.2 MPa, resulting in 100% CO2 conversion. In most of these cases, the catalyst is pre-activated in a H2 stream at temperatures (250-450 °C) to generate the corresponding metal species that function as active centers. In addition to catalysts based on metal particles as active centers, other studies have mentioned metal carbides as active centers in the activation of CO2 (Catal. Lett. 2015, 145, 1365-1373). For example, Corma et al. (JACS 2019, 141, 49, 19304-19311) described a catalyst containing a ruthenium metal core with an outer ruthenium carbide layer. The catalyst was activated at a reaction temperature of 160 °C and atmospheric pressure for 21,428 h. -1 of GHSV, and operates at a H2 / CO2 ratio of 3, 8.8 mol CH4 L -1 h -1 (0.01mol CH4 h -1 ·g cat -1 ) space-time yield of methane is obtained (Patent document ES2828458). Other studies have described the use of transition metal oxides as catalysts for the hydrogenation of CO2 to form methane. For example, HK Pawlak et al. (J. of CO2utilization 2017, 17, 312-319) 、We describe the synthesis of 4-8 nm thin films of nanoparticulate metal oxides, RuO2, Co3O4, Fe3O4, and the mixed oxide RuO2 / Co3O4, for the production of methane from CO2 / H2. In this work, CO2 conversion occurs at reaction temperatures above 200 °C, with a GHSV of 3000 cm2 for RuO2 at 350 °C. 3 h -1 g cat -1 reported a CO2 conversion of 40% at a molar ratio of H2 / CO2 of 4. J. Polanski et al. (Appl. Catal. B. Environ., 2017, 206, 16-23) reported a STY with 100% selectivity to methane at 200°C, H2 / CO2 = 4, and atmospheric pressure. CH4 0.123mol CH4 h -1 reported 100% conversion of CO2 over a catalyst of 1.5 wt% ruthenium oxide (RuO2) supported on nickel oxide (NiO) with a space yield of 100%. However, these catalysts are not stable under the reaction conditions and deactivate over the reaction time. In patent document US4847231A1, X (0>X>2) supported on different metal oxides (TiO2, ZrO2, HfO2, BaTiO3, Al2O3) are claimed to be catalysts for the hydrogenation of CO2 to form methane in the gas phase in the presence or absence of light, operating at low temperatures and pressures and achieving 100% selectivity to methane. x In this case, methane production is 1.7 × 10 at 25°C. -6 mol CH4 h -1 ·g cat -1 and 0.1 × 10 at 90 °C, 1 bar, and in the absence of light. -3 mol CH4 h -1 g cat -1Other studies have reported reaction temperatures below 200 °C for the hydrogenation of CO to form methane, but the methane yields obtained are low. Therefore, DP Becker et al. (Catal. Sci. Technol. 2016, 6, 8117-8128) reported that a Ru / TiO catalyst was synthesized by impregnating a colloidal suspension of RuO nanoparticles in TiO (P25), and the catalyst was found to be 0.003 mol at 165 °C. CH4 h -1 g cat -1 , and 0.009 mol at 200 °C CH4 h -1 g cat -1 yield and contact time of 1.6 ml s -1 ·g -1 (F / W), H2 / CO2 = 4, and atmospheric pressure. Patent document CN111514889A describes that supported ruthenium catalysts using ionic liquids for synthesis enable high dispersion of ruthenium active centers. The document reports high stability and activity at low reaction temperatures. For example, in the case of a ruthenium catalyst supported on SiO2 using [EMIM]Cl as the ionic liquid, the catalyst was pre-activated in H2 at 400 °C for 3 hours, and then activated at 180 °C, a space velocity of 2400 h -1 At a molar ratio of H2:CO2:N2=4:1:5 and 1 bar, a CO2 conversion of 3.7% is obtained.

[0003] In summary, the yields reported to date are low at low reaction temperatures, i.e., below 200 °C, and are as low as 0.02 mol CH4 h -1 g cat -1 is less than.

[0004] The present invention relates to a novel material comprising at least Ru metal, an inorganic matrix, and a novel crystalline phase defined as Ru oxocarbonate, the latter serving as the active phase in the activation of CO. This material is active and selective in the hydrogenation of CO to form methane at low temperatures (below 200°C).

[0005] The application areas include the composition of the active phase of the catalyst, the composition of the catalyst, the method for obtaining the catalyst, and the application of the catalyst for obtaining methane from CO2 by thermal hydrogenation.

[0006] The present invention has the following advantages over the prior art: 1) good activity and selectivity to methane at low temperatures (below 200°C); 2) high stability over time; and 3) the preparation method does not require a pre-activation step of the catalyst precursor at high temperatures.

[0007] Description of the Invention The present invention relates to a catalyst containing a novel crystalline phase of ruthenium oxide, which crystallizes as a monoclinic structure containing carbon in interstitial positions. The crystal structure determined by X-ray diffraction is shown in Figure 1 of the present invention. The crystal structure is monoclinic ruthenium oxide, and the space group is P21 / c. The cell parameters, fractional atomic coordinates, and bond distances are shown in Tables 1-3. Rietveld refinement of the X-ray pattern revealed RuO2C X where X is between 0.3 and 0.8, preferably between 0.4 and 0.8. The presence of carbon in interstitial positions determines the formation of ruthenium oxocarbonate.

[0008] Thus, a first aspect of the present invention relates to a ruthenium catalyst comprising at least: - Ru metal an organic or inorganic matrix, said organic or inorganic matrix being preferably selected from silica, alumina, metal oxides, zeolites, carbon, and combinations thereof, more preferably carbon. Ru oxocarbonate, which serves as the active phase and has the following structure: RuO x C y Here, x is 1 to 3, preferably 1.8 to 2.5. Here, y is from 0.3 to 0.8, preferably from 0.4 to 0.8.

[0009] According to a particular embodiment, said active phase of the above catalyst may further comprise nitrogen in an amount ranging from 0.1 to 0.5 molar ratio, preferably in an amount ranging from 0.2 to 0.4.

[0010] The active phase crystallizes as a monoclinic phase containing carbon in interstitial positions.

[0011] According to a preferred embodiment, the above-mentioned catalyst may further contain a metal, preferably selected from Pd, Co, Ni, In, alkali metals, alkaline earth metals and combinations thereof, in an amount of 0.2 to 98 wt % of the total metal components.

[0012] A second aspect of the present invention relates to a method for obtaining the above-mentioned catalyst. The catalyst may be obtained directly by a process comprising contacting at least a ruthenium catalyst precursor, preferably selected from RuO2, mixtures of RuO2 with organic or inorganic matrices, and mixtures of RuO2 with other metal oxides selected from PdO2, Co3O4, NiO, In2O3, alkali metals, alkaline earth metals and combinations thereof, with a reaction gas mixture comprising at least H2, N2 and CO2.

[0013] As mentioned above, the composition of the catalyst precursor according to the present invention may comprise a single phase, e.g., ruthenium oxide, or two phases, i.e., the catalyst precursor may be selected from RuO2, mixtures of RuO2 with organic or inorganic matrices, and mixtures of RuO2 with other metal oxides selected from PdO2, Co3O4, NiO, In2O3, alkali metals, alkaline earth metals, and combinations thereof.

[0014] According to a preferred embodiment, the catalyst precursor is a mixture of RuO2 and an organic or inorganic matrix, having a weight ratio of 99.9 to 10 RuO2:0.1 to 90 organic or inorganic matrix, more preferably 80 to 50 RuO2:20 to 50 organic or inorganic matrix.

[0015] The catalyst precursor can be a physical mixture of RuO2 and an organic or inorganic matrix, mixed by physical methods such as ball milling or chemical methods such as immersion, co-precipitation, or sol-gel processes.

[0016] According to a particular embodiment, the ratio of RuO2 / organic or inorganic matrix is ​​10:90, preferably 75 to 25.

[0017] According to a particular embodiment, the molar ratio of H2 / CO2 in the reaction gas mixture may be from 1 to 6, preferably from 2 to 4, and more preferably is 3.

[0018] According to a particular embodiment of the method for obtaining the catalyst, the catalyst precursor is brought into direct contact with the reaction gas mixture without first undergoing any preactivation step.

[0019] According to another specific embodiment, the catalyst precursor may be subjected to a hydrothermal process before being contacted with the reaction gas mixture, and the hydrothermal process may be carried out in an autoclave at a temperature of 150 to 250°C, preferably 175 to 200°C, under static conditions for 10 to 30 hours, preferably 18 to 24 hours. Furthermore, the hydrothermal process for providing the catalyst precursor may include an organic compound that may be selected from monosaccharides selected from glucose, mannose, fructose, and xylose, sugar oligomers, organic compounds containing at least two nitrogen atoms (e.g., ethylenediaminetetraacetic acid, chitosan, alginic acid, urea, or combinations thereof), and combinations thereof, and a polar solvent that may be selected from water or a mixture of water and a short-chain alcohol in a volume ratio (v / v) of 1:1 to 5:1, preferably 1:1.

[0020] The catalyst object of the present invention has activity and selectivity in the hydrogenation of CO to form methane at reaction temperatures between 50° C. and 200° C., preferably between 120° C. and 200° C., and more preferably between 150° C. and 190° C. Accordingly, a third aspect of the present invention provides a catalyst for hydrogenation of CO to form methane at temperatures between 120° C. and 200° C., preferably between 150° C. and 190° C., at a high space velocity (GHSV) of 10714 h -1 From 42857h -1 and preferably 12857h -1 From 32142h -1 The present invention relates to the use of the catalyst as described above for the hydrogenation of CO to obtain methane with an amount of hydrogen (H / CO of less than 6, preferably 3) and at a pressure of from atmospheric to 5 MPa. The hydrogenation can be carried out in a fixed bed reactor, a fluidized bed, a slurry reactor or in a membrane reactor.

[0021] According to a particular embodiment, the CO hydrogenation reaction can be carried out in a fixed-bed fluidized reactor with a catalyst particle size of 400-600 μm diluted with SiC (sieved to 600-800 μm) in a weight ratio of (catalyst:SiC)=0.04-0.25, more preferably 0.14.

[0022] The space-time yield (STY) of methane in the present invention (see Example 1) operating at 2 MPa is 24,000 h for the physical mixture RuO2 + C with H2 / CO2 = 3. -1 h -1 117.04 mol at 180°C CH4 L -1 h -1 (31.21 mol h -1 ·g cat -1 These values ​​are significantly higher than those obtained with other conventional catalysts used for the hydrogenation of CO2 to obtain methane. The selectivity towards CH4 is 99.9% in all cases.

[0023] The stability of the catalyst under reaction conditions can be modified by the addition of organic or inorganic matrices or additives and / or reaction conditions (see Examples 1, 2, and 3).

[0024] Tables 1~3: [Table 1]

[0025] [Table 2]

[0026] [Table 3]

[0027] BRIEF DESCRIPTION OF THE DRAWINGS Figure 1. X-ray diffraction of the ruthenium oxocarbonate phase.

[0028] Figure 2. Catalyst precursor A was heated at 180°C, 2 MPa, and a space velocity of 24,000 h -1 The conversion of CO2 by contacting the reactant gas mixture with 23.8 vol% CO2, 71.3 vol% H2, and 5 vol% N2.

[0029] Figure 3. X-ray diffraction of catalyst precursor A and the results at 2 MPa, 180 °C, and a space velocity of 24,000 h -1 X-ray diffraction after subjecting the reactant gas mixture to

[0030] Figure 4. Catalyst precursor A' was tested at 180°C, 2 MPa, and a space velocity of 24,000 h -1 The conversion of CO2 by contacting the reactant gas mixture with 23.8 vol% CO2, 71.3 vol% H2, and 5 vol% N2.

[0031] Figure 5. Catalyst precursor A was tested at 180°C, 0.1 MPa, and a space velocity of 24,000 h -1The conversion of CO2 by contacting the reactant gas mixture with 23.8 vol% CO2, 71.3 vol% H2, and 5 vol% N2.

[0032] Figure 6. Catalyst precursor B was heated at 180°C, 2 MPa, and a space velocity of 24,000 h -1 The conversion of CO2 by contacting the reactant gas mixture with 23.8 vol% CO2, 71.3 vol% H2, and 5 vol% N2.

[0033] Figure 7. Catalyst precursor C was heated at 180°C, 2 MPa, and a space velocity of 24,000 h -1 The conversion of CO2 by contacting the reactant gas mixture with 23.8 vol% CO2, 71.3 vol% H2, and 5 vol% N2.

[0034] Figure 8. Catalyst D (reference catalyst) at 180°C, 2 MPa, and a space velocity of 24,000 h -1 , and the feed gas composition is 23.8 vol% CO2, 71.3 vol% H2, and 5 vol% N2.

[0035] Figure 9. Reference catalyst D at 2 MPa, 180 °C, and a space velocity of 24,000 h -1 X-ray diffraction after subjecting the reactant gas mixture to

[0036] [Description of the embodiment] Example 1. Catalyst Precursor A Catalyst precursor A is a physical mixture of RuO2 (99.9%) (manufactured by Aldrich) and charcoal (Norit) in a weight ratio of 75:25. The mixture is prepared by mixing both components in a mortar for 30 minutes. X-ray diffraction patterns show that the particle size of RuO2 is approximately 38 nm.

[0037] Example 2. Catalytic behavior of catalyst precursor A in contact with reaction gas at 2 MPa (Figure 2) The catalytic behavior of the catalyst is tested in a stainless steel fixed-bed reactor with an internal diameter of 11 mm and a length of 240 mm. 260 mg of catalyst precursor (particle size 400-600 μm) is diluted with 6300 mg of SiC (particle size 600-800 μm). The volume occupied by the catalyst precursor is 0.28 cm. 3 No pre-activation is required. The resulting mixture was stirred at 23.8 ml min -1 CO 2、 71.3ml min -1 of H2, and 5 ml min -1 The space velocity is 24,000 h -1 The temperature was 180°C and the pressure was 2 MPa. Multiple analyses were performed for 15 minutes each, for a total reaction time of 5475 minutes. Figure 2 shows the results at 180°C, 2 MPa, and 24000 h. -1 The time evolution of the CO2 conversion at 1000 s is shown. The selectivity to methane is 99.9%.

[0038] The data in Figure 2 show that under steady-state conditions, approximately 50% conversion of CO2 and a methane yield of 117.04 mol CH4 L -1 h -1 (31.21 μmol·s -1 ·g cat -1 ) corresponds to The X-ray diffraction of the catalyst after subjecting the catalyst precursor to the reaction gas mixture is shown in Figure 3. Peaks associated with the ruthenium oxocarbonate phase are indicated with an asterisk.

[0039] Example 3. Catalyst Precursor A' Catalyst precursor A' is a physical mixture of RuO2 (99.9%) (Aldrich) and SiO2 (99.5%) (Aldrich) in a weight ratio of 75:25. The mixture is prepared by mixing both components in a mortar for 30 minutes. X-ray diffraction patterns show that the particle size of RuO2 is approximately 38 nm. The particle size of SiO2 is 5-12 nm.

[0040] Example 4. Catalytic behavior of catalyst precursor A' in contact with reaction gas at 2 MPa (Figure 4) The catalytic behavior of this catalyst is tested in the same reactor configuration as in Example 2. 260 mg of catalyst precursor (particle size 400-600 μm) is diluted with 6300 mg of SiC (particle size 600-800 μm). The resulting mixture is stirred at 23.8 ml min -1 of CO2, 71.3ml min -1 of H2, and 5 ml min -1 Contact with N2 。 Space velocity is 24,000 h -1 The temperature is 180°C and the pressure is 2 MPa. The reaction products are subjected to online GC analysis (SCION-456-GC) using an MS-13X column and a BR-Q Plot column for the TCD and FID detectors, respectively. Multiple analyses are performed for 15 minutes each, for a total reaction time of 1200 minutes. Figure 4 shows the results of the reaction at 180°C, 2 MPa, and 24000 h. -1 The time evolution of the CO2 conversion at 1000 s is shown. The selectivity to methane is 99.9%.

[0041] The data in FIG. 4 show higher deactivation than observed in Example 2.

[0042] Example 5. Catalytic behavior of catalyst precursor A in contact with reaction gas at 0.1 MPa (Figure 5) The catalytic behavior of this catalyst is tested in the same reactor configuration as in Example 2. 260 mg of catalyst precursor (particle size 400-600 μm) is diluted with 6300 mg of SiC (particle size 600-800 μm). The resulting mixture is stirred at 23.8 ml min -1 CO 2、 71.3ml min -1 of H2, and 5 ml min -1 The space velocity is 24,000 h -1 The temperature was 180°C and the pressure was 0.1 MPa. Multiple analyses were performed for 15 minutes each, for a total reaction time of 200 minutes. Figure 5 shows the results at 180°C, 0.1 MPa, and 24000 h. -1 The time evolution of the CO2 conversion at 1000 s is shown. The selectivity to methane is 99.9%.

[0043] The data in Figure 5 show that under steady-state conditions, a 7.5% conversion of CO2 and a methane yield of 17.55 mol CH4 L -1 h -1 (4.68 μmol s -1 g cat -1 ) clearly shows the effect of pressure corresponding to

[0044] Example 6. Catalyst Precursor B Catalyst precursor B was obtained by subjecting a catalyst precursor of RuO2 (Aldrich) to hydrothermal conditions. Specifically, 120 mg of glucose (Aldrich), 7 ml of Milli-Q water, and 100 mg of RuO2 (Aldrich) were mixed ultrasonically for 20 minutes. The resulting mixture was transferred to a 12.5 ml autoclave. The autoclave was placed in an oven at 175 °C and kept stationary for 24 hours. After removing from the oven, the mixture was allowed to cool to room temperature for 2 hours. The contents were filtered and washed with distilled water until no bubbles were observed, and finally with acetone. The resulting solid was dried in an oven at 60 °C for 12 hours.

[0045] Example 7. Catalytic behavior of catalyst precursor B in contact with reaction gas at 2 MPa (Figure 6) The catalytic behavior of this catalyst is tested in the same reactor configuration as in Example 2. 260 mg of catalyst precursor (particle size 400-600 μm) is diluted with 6300 mg of SiC (particle size 600-800 μm). The resulting mixture is stirred at 23.8 ml min -1 of CO2, 71.3ml min -1 of H2, and 5 ml min -1 The space velocity is 24,000 h -1 The temperature was 180°C and the pressure was 2 MPa. Multiple analyses were performed for 15 minutes each, for a total reaction time of 15,769 minutes. Figure 6 shows the results at 180°C, 2 MPa, and 24,000 h -1 The time evolution of the CO2 conversion at 1000 s is shown. The selectivity to methane is 99.9%.

[0046] The data in Figure 6 show that under steady-state conditions, the CO2 conversion is approximately 40% and the methane yield is 91.63 mol CH4 L -1 h -1 (24.50 μmol s -1 g cat -1 ) corresponds to

[0047] Example 8. Catalyst Precursor C Dissolve 1.12 g of RuCl3.xH2O (Johnson Mattey, 40.7 wt% Ru) in 120 ml of Milli-Q water. Add 8 ml of octanoic acid (Sigma Aldrich, >98%) dropwise. Under stirring, adjust the pH to approximately 8 by slowly adding 1.5 M NaOH solution (Scharlau). Then, heat the mixture to 80°C for 1 hour with continuous stirring. Filter the supernatant under vacuum and wash first with water (until all chlorides are removed and the mother liquor is neutralized), then three times with ethanol.

[0048] Finally, the resulting solid is dried in an oven at 100 °C for 3 h and calcined in a muffle furnace at 950 °C for 4 h (3 °C / min). The X-ray diffraction pattern of the final solid corresponds to RuO with a particle size of approximately 62.4 nm. The resulting material is used directly in the reaction and is designated as catalyst precursor C.

[0049] Example 9. Catalytic behavior of catalyst precursor C in contact with reaction gas at 2 MPa (Figure 7) The catalytic behavior of this catalyst is tested in the same reactor configuration as in Example 2. 260 mg of catalyst precursor (particle size 400-600 μm) is diluted with 6300 mg of SiC (particle size 600-800 μm). The resulting mixture is stirred at 23.8 ml min -1 of CO2, 71.3ml min -1 of H2, and 5 ml min -1 The space velocity is 24,000 h -1The temperature was 180°C and the pressure was 2 MPa. Multiple analyses were performed for 15 minutes each, for a total reaction time of 9000 minutes. Figure 7 shows the results at 180°C, 2 MPa, and 24000 h. -1 The time evolution of the CO2 conversion at 1000 s is shown. The selectivity to methane is 99.9%.

[0050] The data in Figure 7 show that under steady-state conditions, the CO2 conversion is approximately 50% and the methane yield is 117.04 mol CH4 L -1 h -1 (31.21 μmol·s -1 ·g cat -1 ) corresponds to

[0051] Example 10. Catalyst D Catalyst D was Ru manufactured by Sigma-Aldrich. 0 Catalyst D is ruthenium black. According to the X-ray diffraction pattern, the particle size is about 21 nm. Catalyst D is mixed with charcoal (Norit) in a mortar by physical means in a weight ratio of 75:25.

[0052] Example 10. Catalytic behavior of reference catalyst D at 2 MPa (FIG. 8) The catalytic behavior of Reference Catalyst D is tested in the same reactor configuration as in Example 2. The catalyst is heated at 260 °C for 2 hours in a 20 vol% H, 80 vol% N mixture at atmospheric pressure, 100 ml min -1 The reaction mixture is then subjected to a preactivation process in a fluid with a total flow rate of 23.8 ml min at 100°C and 2 MPa. -1 of CO2, 71.3ml min -1 of H2, and 5 ml min -1 Switch to N2. Space velocity is 24000h -1 Then, the temperature is increased to 180°C (10°C min -1 ) is raised to 180°C, 2 MPa, and 24,000 h. -1 The time evolution of the CO2 conversion at 1000 s is shown. The selectivity to methane is 99.9%.

[0053] The data in Figure 8 show a conversion of 0.54% of CO2 and a methane yield of 1.23 mol CH4 L -1 h -1 (0.33 μmol·s -1 ·g cat -1 ), which is significantly lower than the yield shown in Example 2.

[0054] The X-ray diffraction of Catalyst D after being subjected to the reaction gas mixture is shown in Figure 9. No peaks associated with the ruthenium oxocarbonate phase are detected. The only peak detected corresponds to ruthenium metal. [Brief explanation of the drawings]

[0055] [Figure 1] FIG. 1 shows the X-ray diffraction of the ruthenium oxocarbonate phase. [Figure 2] Figure 2 shows the conversion of CO2 by contacting catalyst precursor A with a reaction gas mixture at 180 °C, 2 MPa, and a space velocity of 24,000 h-1, where the reaction gas composition was 23.8 vol% CO2, 71.3 vol% H2, and 5 vol% N2. [Figure 3] FIG. 3 shows the X-ray diffraction of catalyst precursor A and after being subjected to the reaction gas mixture at 2 MPa, 180° C., and a space velocity of 24,000 h −1 . [Figure 4] Figure 4 shows the CO2 conversion rate by contacting catalyst precursor A' with a reaction gas mixture at 180 °C, 2 MPa, and a space velocity of 24,000 h-1, where the reaction gas composition was 23.8 vol% CO2, 71.3 vol% H2, and 5 vol% N2. [Figure 5] Figure 5 shows the conversion of CO2 by contacting catalyst precursor A with a reaction gas mixture at 180 °C, 0.1 MPa, and a space velocity of 24,000 h-1, where the reaction gas composition was 23.8 vol% CO2, 71.3 vol% H2, and 5 vol% N2. [Figure 6]FIG. 6 shows the conversion of CO2 by contacting catalyst precursor B with a reaction gas mixture at 180 °C, 2 MPa, and a space velocity of 24,000 h-1, where the reaction gas composition was 23.8 vol% CO2, 71.3 vol% H2, and 5 vol% N2. [Figure 7] Figure 7 shows the conversion of CO2 by contacting catalyst precursor C with a reaction gas mixture at 180 °C, 2 MPa, and a space velocity of 24,000 h-1, where the reaction gas composition was 23.8 vol% CO2, 71.3 vol% H2, and 5 vol% N2. [Figure 8] Figure 8 shows the CO2 conversion rate for reference catalyst D at 180°C, 2 MPa, and a space velocity of 24,000 h-1, with a feed gas composition of 23.8 vol% CO2, 71.3 vol% H2, and 5 vol% N2. [Figure 9] FIG. 9 shows the X-ray diffraction of Reference Catalyst D after being subjected to a reaction gas mixture at 2 MPa, 180° C., and a space velocity of 24,000 h −1 .

Claims

1. A ruthenium catalyst characterized in that it comprises at least: - Ru metal - organic or inorganic matrix - Ru oxocarbonate, which serves as the active phase and has the following structure: RuO ｘ C ｙ where x is from 1 to 3 and y is from 0.3 to 0.

8.

2. Catalyst according to claim 1, characterized in that the active phase further comprises nitrogen in an amount of 0.1 to 0.5 molar ratio.

3. 3. The catalyst according to claim 1, wherein the oxocarbonate phase crystallizes as a monoclinic phase containing carbon in interstitial positions.

4. Catalyst according to any one of the preceding claims, characterized in that the organic matrix or the inorganic matrix is ​​selected from silica, alumina, metal oxides, zeolites, carbon, and combinations thereof.

5. Catalyst according to claim 4, characterized in that the organic matrix is ​​carbon.

6. 10. The catalyst of any one of the preceding claims, further comprising a metal selected from Pd, Co, Ni, In, alkali metals, alkaline earth metals and combinations thereof.

7. A process for obtaining a catalyst according to any one of the preceding claims, comprising the steps of: treating at least a ruthenium catalyst precursor with at least H ２ , N ２ and CO ２ with a reaction gas mixture comprising:

8. The catalyst precursor is RuO ２ , RuO ２ and a mixture of RuO with an organic or inorganic matrix, ２ and PdO ２ , Co ３ O ４ , NiO, In ２ O ３ 8. A process for obtaining a catalyst according to claim 7, characterized in that the oxides are selected from the group consisting of oxides of alkali metals, alkaline earth metals and mixtures thereof with other metal oxides selected from the group consisting of alkali metals, alkaline earth metals and combinations thereof.

9. The catalyst precursor is RuO ２ and an organic or inorganic matrix, ２ 9. A process for obtaining a catalyst according to claim 7, characterized in that the catalyst has a weight ratio of organic or inorganic matrix of from 0.1 to 90.

10. H in the reaction gas mixture ２ / CO ２ 10. A process for obtaining a catalyst according to any one of the preceding claims, characterized in that the molar ratio of

11. The use of the catalysts according to claims 1 to 6 and the method according to claims 7 to 10 at a temperature of 50°C to 200°C and 10714h. －１ From 42857h －１ H2 (H ２ / CO ２ less than 6) and atmospheric pressure to 5 MPa, ２ Use of the catalyst obtained by the process for obtaining methane by hydrogenation of

12. CO ２ 12. Use of the catalyst according to claim 11, characterized in that the hydrogenation reaction of is carried out in a fixed bed reactor, a fluidized bed, a slurry reactor or in a membrane reactor.

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