A CO low-temperature selective methanation bimetallic catalyst and its preparation method and application

Abstract

The present invention belongs to the field of heterogeneous catalysis and discloses a low-temperature selective methanation bimetallic catalyst for CO, its preparation method, and application. The present invention discloses a low-temperature selective methanation bimetallic catalyst for CO, comprising Ru and Ni as active components and a NiTi-LDH support. The catalyst is simple to prepare, uses a low amount of the precious metal Ru, exhibits excellent low-temperature activity, and can deeply remove CO from hydrogen-rich gas to below 10 ppm at 180-260°C with a reaction selectivity exceeding 50%. It can be used for the deep removal of trace CO from hydrogen-rich gas.

Description

Technical Field

[0001] The present invention belongs to the field of heterogeneous catalysis, and particularly relates to a CO low-temperature selective methanation bimetallic catalyst, a preparation method and an application thereof. Background Art

[0002] Proton exchange membrane fuel cells (PEMFCs) offer advantages such as high efficiency, low pollution, low operating temperature, fast startup, and high power density, making them promising for applications in new energy vehicles and distributed power generation. PEMFCs primarily use hydrogen or hydrogen-rich gas as fuel. Hydrogen fuel is primarily produced by reforming hydrogen-rich compounds such as methane, methanol, and dimethyl ether, followed by a water-gas shift reaction. However, this method produces hydrogen fuel containing 20 vol.% CO2 and 0.5-2 vol.% CO. Even trace amounts of CO can poison the Pt anode material in PEMFCs, reducing cell performance. To ensure proper operation and extend the life of PEMFCs, deep CO removal from the hydrogen fuel is necessary. Currently, effective chemical methods for deep CO removal include CO selective methanation (CO-SMET) and CO selective oxidation. Compared to CO selective oxidation, CO selective methanation does not require the introduction of oxygen or air into the system, resulting in a simpler process. Furthermore, nitrogen is not introduced into the hydrogen fuel to reduce the hydrogen content. Currently, the challenge in CO selective methanation lies in the development of highly active and selective catalysts.

[0003] The active components for CO selective methanation are usually the noble metal Ru and the non-noble metal Ni. The noble metal Ru has good catalytic activity under low temperature conditions, while the non-noble metal Ni has problems such as difficulty in reducing the active component, high reaction temperature, and easy agglomeration and sintering. TiO2 has semiconductor properties and can produce strong metal-support interactions with the supported metal. Tada et al. (Effect of metal addition to Ru / TiO2 catalyst on selective CO methanation. Catalysis Today, 2014, 232:16-21.) et al. directly loaded 5wt% Ru and Ni onto commercial TiO2 and were able to reduce the CO outlet concentration to below 500ppm in the range of 200℃-290℃. Li et al. (Hydrogenated TiO2 supported Ru for selective methanation of CO in practical conditions. Applied Catalysis B: Environmental, 2021, 298: 120597) calcined TiO2 in a hydrogen atmosphere at 400 ° C for 3 h to obtain a modified H2-TiO2, and then loaded 1.1 wt% Ru to obtain a Ru / H2-TiO2 catalyst, which can reduce CO to below 10 ppm in the range of 200-260 ° C while maintaining a selectivity of more than 50%. Ping et al. (Ni-doped TiO2 nanotubes supported Rucatalysts for CO selective methanation in H2-rich reformate gases. Reaction Kinetics Mechanisms & Catalysis, 2018.) loaded 1 wt% Ru and 5 wt% Ni onto titanium nanotubes (TNT) to prepare a Ru / Ni-TNT catalyst, which can reduce the CO outlet concentration to below 10 ppm in the range of 210-270 ° C while maintaining a selectivity of more than 50%. Xiao Gang et al. (authorization announcement number: CN101607198B) loaded 0.2-2wt% Ru onto a composite oxide support of ZrO2 and CeO2. The resulting Ru / ZrO2-CeO2 had good activity within the temperature range of 220℃-300℃, but could only reduce the CO outlet concentration to 25ppm.Dong Xinfa et al. (authorization announcement number: CN113398935B) synthesized graphene oxide-nickel aluminum hydrotalcite hydrogel by layer-by-layer self-assembly, and obtained a graphene-composite metal oxide aerogel carrier through freeze-drying and calcination, and loaded Ru on it. The Ru-Ni / rGO-MMO obtained after calcination can reduce the outlet concentration of hydrogen-rich gas containing 1 vol% CO to below 10 ppm at 220-290°C, while maintaining a selectivity of more than 50%.

[0004] The catalysts prepared by the above methods generally have shortcomings such as large amount of precious metal Ru (Ru amount greater than or equal to 1wt%), poor low-temperature activity (reaction window starting temperature is higher than 200°C), incomplete CO reaction (CO outlet concentration fails to drop below 10ppm). Summary of the Invention

[0005] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the primary object of the present invention is to provide a bimetallic catalyst for the low-temperature selective methanation of CO.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned CO low-temperature selective methanation bimetallic catalyst.

[0007] Another object of the present invention is to provide an application of the above-mentioned CO low-temperature selective methanation bimetallic catalyst for deep removal of trace CO in hydrogen-rich gas.

[0008] The purpose of the present invention is achieved through the following solutions:

[0009] A low-temperature selective methanation bimetallic catalyst for CO is a metal-supported catalyst with Ru and Ni as active components and nickel-titanium hydrotalcite (NiTi-LDH) as a carrier, wherein the active components are derived from Ru reduced by ruthenium salt and Ni partially reduced in NiTi-LDH.

[0010] The molar ratio of Ni to Ti in the NiTi-LDH is 2-3; the loading amount of Ru is 0.3wt%-1.2wt% of the NiTi-LDH; preferably, the loading amount of Ru is 0.3wt%.

[0011] The preparation method of the above-mentioned CO low-temperature selective methanation bimetallic catalyst includes the following steps: preparing a NiTi-LDHs catalyst carrier by a coprecipitation method, then loading the active component Ru by an impregnation method, and obtaining a Ru-Ni / NiTi-LDH catalyst after drying and reduction.

[0012] The preparation method of the above-mentioned CO low-temperature selective methanation bimetallic catalyst specifically comprises the following steps:

[0013] (1) Preparation of NiTi-LDH carrier by co-precipitation method: nickel salt is dissolved in water to obtain nickel salt solution (I); TiCl4 is mixed with concentrated hydrochloric acid to obtain a colorless or yellow clear solution (II); solution (II) is added to solution (I) to obtain a mixed solution (III); a mixed solution of NaOH and Na2CO3 (IV) is prepared as a precipitant; solution (IV) is added to solution (III), stirred evenly until complete precipitation, the precipitate is aged, filtered, and dried to obtain a solid NiTi-LDH carrier;

[0014] (2) The NiTi-LDH carrier obtained in step (1) is immersed in a ruthenium salt solution, and then dried and reduced to obtain the Ru-Ni / NiTi-LDH catalyst.

[0015] The nickel salt in step (1) is one or more of nickel chloride, nickel nitrate, and nickel oxalate; the nickel in the solution (I) is 2+ The concentration is 0.1-0.4 mol·L -1 , preferably Ni 2+ The concentration is 0.3 mol·L -1 .

[0016] The mass fraction of concentrated hydrochloric acid in the solution (II) of step (1) is 36%-38%, preferably 37%; the volume ratio of TiCl4 to concentrated hydrochloric acid is 0.5-1, preferably the volume ratio of TiCl4 to concentrated hydrochloric acid is 0.5.

[0017] The total concentration of metal cations in the mixed solution (III) of step (1) is 0.2-0.5 mol·L -1 , Ni 2+ With Ti 4+ The molar ratio is 2-3:1. Preferably, the cation concentration in the solution is 0.4 mol·L -1 , Ni 2+ With Ti 4+ The molar ratio is 3:1.

[0018] Na in the precipitant of step (1) + The total concentration is 1.2-1.6 mol·L -1 The molar ratio of Na2CO3 to NaOH is 0.3-0.5:1. Preferably, Na + The total concentration is 1.2-1.4 mol·L -1 , the molar ratio of Na2CO3 to NaOH is 0.375-0.5:1.

[0019] The pH of the mixed solution during complete precipitation in step (1) is 9.0-10.0, preferably, the pH is 9.5 during complete precipitation.

[0020] The aging time in step (1) is 20-30 hours, and the aging temperature is 80-95°C; preferably, the aging time is 24 hours, and the aging temperature is 90°C.

[0021] The ruthenium salt in step (2) is ruthenium trichloride or ruthenium acetate, preferably ruthenium trichloride; Ru in the ruthenium salt solution 3+ Concentration 0.2-0.82 mg mL -1 , preferably 0.204 mg·mL -1 .

[0022] The immersion temperature in step (2) is room temperature; the immersion time is 12-24 hours, and the preferred immersion time is 20 hours.

[0023] The drying temperatures in step (1) and step (2) are both 50°C-70°C, preferably 60°C.

[0024] The reducing gas composition of step (2) is V N2 :V H2 =1:0.8-1.2:1, preferably V N2 :N H2 =1:1; reducing gas space velocity is 6000-7200mL·h -1 ·g -1 Preferably, the reducing gas space velocity is: 7200 mL·h -1 ·g -1

[0025] The reduction temperature in step (2) is 330-370° C., preferably 350° C.; the reduction time is 1-3 h, preferably 1.5 h.

[0026] The above-mentioned CO low-temperature selective methanation bimetallic catalyst is used to deeply remove trace CO from hydrogen-rich gas, wherein the CO concentration in the hydrogen-rich gas is 0.5-1 vol.%.

[0027] Furthermore, the reaction temperature of the catalyst when removing trace CO is 180°C-260°C.

[0028] The mechanism of the present invention is:

[0029] The present invention provides a preparation method and application of a Ru-Ni / NiTi-LDH supported bimetallic catalyst with NiTi-LDH as a carrier and the synergistic effect of precious metal Ru and non-precious metal Ni. Ru-Ni / NiTi-LDH has a flaky structure, and the cations on the hydrotalcite layer can be evenly distributed, so that the dispersion of Ni on the catalyst surface is high. There is a hydrogen overflow effect between Ru and Ni on the catalyst surface. The reduction temperature of RuCl3 is relatively low. During the reduction process, Ru is reduced first, and H2 first dissociates into active H* on Ru, and then overflows onto NiO, so that NiO is reduced at a lower temperature, lowering the reduction temperature of Ni, allowing more Ni to be reduced, and significantly improving the activity of the catalyst. The catalyst prepared by the present invention can reduce the concentration of CO in hydrogen-rich gas to below 10 ppm within a relatively low reaction temperature and a wide reaction window (180-260°C), and the selectivity is higher than 50%, which better meets the requirements of fuel cell electric vehicles for high-quality hydrogen source fuel.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] The present invention first introduces Ni and Ti elements into hydrotalcite to produce a NiTi-LDH support. Ru is then loaded onto the NiTi-LDH support to produce a Ru-Ni / NiTi-LDH catalyst. This catalyst, with a Ru loading as low as 0.3 wt%, can reduce the outlet concentration of 1 vol.% CO to below 10 ppm within a temperature window of 180°C to 260°C, while maintaining selectivity above 50%.

[0032] (1) The Ru-Ni / NiTi-LDH bimetallic catalyst for CO selective methanation of the present invention has good low-temperature activity. Under the synergistic effect of the Ni and Ru bimetallics, CO in hydrogen-rich gas can be reduced to below 10 ppm within a wide reaction temperature window of 180-260°C, with a selectivity higher than 50%.

[0033] (2) The Ru-Ni / NiTi-LDH bimetallic catalyst for CO selective methanation of the present invention is inexpensive and economical. The active components in the catalyst are composed of Ni and the noble metal Ru, but the loading amount of the noble metal Ru only needs to be about 0.3 wt.%.

[0034] (3) There is a hydrogen overflow effect between Ru and NiO on the Ru-Ni / NiTi-LDH bimetallic catalyst for CO selective methanation of the present invention, and the required reduction temperature is low.

[0035] (4) The layered structure of LDH in the Ru-Ni / NiTi-LDH bimetallic catalyst for CO selective methanation of the present invention plays a confining role and can increase the dispersion of the active component Ni. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 XRD patterns of hydrotalcite supports with different nickel-titanium ratios.

[0037] Figure 2 This is a curve chart showing the change of CO and CH4 concentrations with temperature in the CO selective methanation reaction over the catalyst in Comparative Example 1.

[0038] Figure 3 This is a curve chart showing the change of CO and CH4 concentrations with temperature in the CO selective methanation reaction over the catalyst of Comparative Example 2.

[0039] Figure 4 This is a curve chart showing the change in CO and CH4 concentrations with temperature in the CO selective methanation reaction over the catalyst in Example 1.

[0040] Figure 5 This is a curve chart showing the change in CO and CH4 concentrations with temperature in the CO selective methanation reaction over the catalyst of Example 2-5. DETAILED DESCRIPTION

[0041] The present invention will be described in further detail below with reference to the Examples and accompanying drawings, but the embodiments of the present invention are not limited thereto. Where specific conditions are not specified in the Examples, conventional conditions or conditions recommended by the manufacturer were followed. Reagents or instruments used, where the manufacturer is not specified, are commercially available conventional products.

[0042] Unless otherwise specified, all reagents used in the examples can be purchased from the market.

[0043] Catalyst performance test method: The catalyst was pelletized and crushed, and 0.2 g of the catalyst with a mesh size of 40-60 was selected and loaded into a quartz reaction tube with an inner diameter of 6 mm. The reaction was carried out at a space velocity of 6000 mL·g -1 ·h -1 A mixed gas containing 79 vol% H2, 20 vol.% CO2, and 1 vol.% CO was introduced, and the reaction temperature was 150°C-320°C. The reaction product was dried and detected online by gas chromatography.

[0044] Comparative Example 1

[0045] 8.724 g of Ni(NO3)2·6H2O was added to 100 mL of deionized water and dissolved to obtain Ni(NO3)2 solution. In an ice-water bath, 1.09 mL of 9.084 mol·L -1The TiCl4 was quickly added dropwise to 3.8 mL of concentrated hydrochloric acid to form a TiCl4 solution; the TiCl4 solution was added dropwise to the Ni(NO3)2 solution and stirred at room temperature for 3 hours. 6.3594 g of Na2CO3 and 6.4 g of NaOH were weighed, added to 200 mL of deionized water, stirred at room temperature, and prepared as a precipitant. The precipitant was then slowly added dropwise to the mixture of TiCl4 and Ni(NO3)2, stirring while adding until the pH of the solution reached 9.5, to obtain a green suspension. The suspension was aged at 90°C for 24 hours. The obtained green precipitate was filtered, washed, and then dried at 60°C to obtain NiTi-LDH with a nickel-titanium ratio of 3. Its XRD spectrum is shown in detail. Figure 1 Curve a, where Figure 1 PDF#15-0087 is a standard card for hydrotalcite.

[0046] Take 0.2g NiTi-LDH with a nickel-titanium ratio of 3 and heat it at a space velocity of 7200mL·h -1 ·g -1 The activity of the catalyst was evaluated after reduction in a mixture of 50 vol% H2 and 50 vol% N2 at 350 °C for 1.5 h. The catalyst test results are shown in Figure 2 ,Depend on Figure 2 It can be seen that NiTi-LDH with a nickel-titanium ratio of 3 can reduce the CO outlet concentration to below 10 ppm at 180°C-220°C while maintaining a selectivity of more than 50%.

[0047] Comparative Example 2

[0048] (1) Add 2.9079 g of Ni(NO3)2·6H2O to 100 mL of deionized water and dissolve it completely to obtain Ni(NO3)2 solution. In an ice-water bath, add 1.09 mL of 9.084 mol·L -1 The TiCl4 was quickly added dropwise to 3.8 mL of concentrated hydrochloric acid to form a TiCl4 solution; the TiCl4 solution was added dropwise to the Ni(NO3)2 solution and stirred thoroughly at room temperature for 3 hours. Weigh 6.3594 of Na2CO3 and 3.2 g of NaOH, dissolve them with 200 mL of deionized water, dissolve them at room temperature, and prepare an alkaline solution. The alkaline solution was then slowly added dropwise to the mixture of TiCl4 and Ni(NO3)2, stirring while adding until the pH of the solution was 9.5, to obtain a green suspension. The suspension was aged at 90°C for 24 hours. The obtained green precipitate was filtered, washed, and then dried at 60°C to obtain NiTi-LDH with a nickel-titanium ratio of 1. Its XRD spectrum is shown in detail. Figure 1 Curve c.

[0049] (2) Use a pipette to measure 3 mL of RuCl3 solution (Ru 3+ The concentration is 0.338 mg·mL -1 0.2 g of NiTi-LDH support with a nickel-titanium ratio of 1 was placed in a RuCl3 solution, immersed for 20 h at room temperature, and then dried at 60 °C. -1 ·g -1 The Ru-Ni / NiTi-LDHs catalyst was obtained by reducing the Ru-Ni / NiTi-LDHs catalyst in a mixture of 50 vol% H2 and 50 vol% N2 at 350°C for 1.5 h, wherein the nickel-titanium ratio was 1 and the Ru loading amount was 0.5 wt% of the mass of the NiTi-LDH.

[0050] The performance of the catalyst was evaluated from Figure 3 It can be seen that the catalyst prepared in this example can reduce the CO outlet concentration to below 10 ppm at 210° C.-240° C. while maintaining a selectivity of more than 50%.

[0051] Example 1

[0052] (1) Add 5.8158 g of Ni(NO3)2·6H2O to 100 mL of deionized water and dissolve it completely to obtain Ni(NO3)2 solution. In an ice-water bath, add 1.09 mL of 9.084 mol· / L Ni(NO3)2 solution to the solution. -1 The TiCl4 was quickly added dropwise to 3.8 mL of concentrated hydrochloric acid to form a TiCl4 solution; the TiCl4 solution was added dropwise to the Ni(NO3)2 solution and stirred thoroughly at room temperature for 3 hours. 6.3594 g of Na2CO3 and 4.8 g of NaOH were weighed, dissolved with 200 mL of deionized water, dissolved at room temperature, and configured into an alkaline solution. The alkaline solution was then slowly added dropwise to the mixture of TiCl4 and Ni(NO3)2, stirring while adding until the pH of the solution was 9.5, to obtain a green suspension. The suspension was aged at 90°C for 24 hours. The obtained green precipitate was filtered, washed, and then dried at 60°C to obtain NiTi-LDH with a nickel-titanium ratio of 2. Its XRD spectrum is shown in detail. Figure 1 Curve b.

[0053] (2) Use a pipette to measure 3 mL of RuCl3 solution (Ru 3+ The concentration is 0.338 mg·mL -1 0.2 g of NiTi-LDH support with a nickel-titanium ratio of 2 was placed in a RuCl3 solution, immersed for 20 h at room temperature, and then dried at 60 °C. -1 ·g -1The Ru-Ni / NiTi-LDHs catalyst was obtained by reducing the Ru-Ni / NiTi-LDHs catalyst in a mixture of 50 vol% H2 and 50 vol% N2 at 350°C for 1.5 h, wherein the nickel-titanium ratio was 2 and the Ru loading was 0.5 wt% of the mass of the NiTi-LDHs.

[0054] The performance of the catalyst was evaluated from Figure 4 It can be seen that the catalyst prepared in this example can reduce the CO outlet concentration to below 10 ppm at 190° C.-260° C. while maintaining a selectivity of more than 50%.

[0055] Example 2

[0056] (1) Add 8.724 g of Ni(NO3)2·6H2O to 100 mL of deionized water and dissolve it completely to obtain Ni(NO3)2 solution. In an ice-water bath, add 1.09 mL of 9.084 mol·L -1 The TiCl4 was quickly added dropwise to 3.8 mL of concentrated hydrochloric acid to form a TiCl4 solution; the TiCl4 solution was added dropwise to the Ni(NO3)2 solution and stirred thoroughly at room temperature for 3 hours. 6.3594 g of Na2CO3 and 6.4 g of NaOH were weighed, dissolved with 200 mL of deionized water, dissolved at room temperature, and configured into an alkaline solution. The alkaline solution was then slowly added dropwise to the mixture of TiCl4 and Ni(NO3)2, stirring while adding until the pH of the solution was 9.5, to obtain a green suspension. The suspension was aged at 90°C for 24 hours. The obtained green precipitate was filtered, washed, and then dried at 60°C to obtain NiTi-LDH with a nickel-titanium ratio of 3. Its XRD spectrum is shown in detail. Figure 1 Curve a.

[0057] (2) Use a pipette to measure 3 mL of RuCl3 solution (Ru 3+ The concentration is 0.204 mg mL -1 0.2 g of NiTi-LDH support with a nickel-titanium ratio of 3 was placed in a diluted RuCl3 solution, immersed for 20 h at room temperature, and then dried at 60 °C. -1 ·g -1 The Ru-Ni / NiTi-LDHs catalyst was obtained by reducing the Ru-Ni / NiTi-LDHs catalyst in a mixture of 50 vol% H2 and 50 vol% N2 at 350°C for 1.5 h, wherein the nickel-titanium ratio was 3 and the Ru loading was 0.3 wt% of the mass of the NiTi-LDH.

[0058] The performance of the catalyst was evaluated from Figure 5It can be seen that the catalyst prepared in this example can reduce the CO outlet concentration to below 10 ppm at 180° C.-260° C. while maintaining a selectivity of more than 50%.

[0059] Example 3

[0060] (1) Add 8.724 g of Ni(NO3)2·6H2O to 100 mL of deionized water and dissolve it completely to obtain Ni(NO3)2 solution. In an ice-water bath, add 1.09 mL of 9.084 mol·L -1 The TiCl4 was quickly added dropwise to 3.8 mL of concentrated hydrochloric acid to form a TiCl4 solution; the TiCl4 solution was added dropwise to the Ni(NO3)2 solution and stirred thoroughly at room temperature for 3 hours. 6.3594 g of Na2CO3 and 6.4 g of NaOH were weighed, dissolved with 200 mL of deionized water, dissolved at room temperature, and configured into an alkaline solution. The alkaline solution was then slowly added dropwise to the mixture of TiCl4 and Ni(NO3)2, stirring while adding until the pH of the solution was 9.5, to obtain a green suspension. The suspension was aged at 90°C for 24 hours. The obtained green precipitate was filtered, washed, and then dried at 60°C to obtain NiTi-LDH with a nickel-titanium ratio of 3. Its XRD spectrum is shown in detail. Figure 1 Curve a.

[0061] (2) Use a pipette to measure 3 mL of RuCl3 solution (Ru 3+ The concentration is 0.338 mg·mL -1 0.2 g of NiTi-LDH support with a nickel-titanium ratio of 3 was placed in a RuCl3 solution, immersed for 20 h at room temperature, and then dried at 60 °C. -1 ·g -1 The Ru-Ni / NiTi-LDHs catalyst was obtained by reducing the Ru-Ni / NiTi-LDHs in a mixture of 50 vol.% H2 and 50 vol.% N2 at 350°C for 1.5 hours, wherein the nickel-titanium ratio was 3 and the Ru loading was 0.5 wt% of the mass of the NiTi-LDHs.

[0062] The performance of the catalyst was evaluated from Figure 5 It can be seen that the catalyst prepared in this example can reduce the CO outlet concentration to below 10 ppm at 180° C.-260° C. while maintaining a selectivity of more than 50%.

[0063] Example 4

[0064] (1) Add 8.724 g of Ni(NO3)2·6H2O to 100 mL of deionized water and dissolve it completely to obtain Ni(NO3)2 solution. In an ice-water bath, add 1.09 mL of 9.084 mol·L -1 The TiCl4 was quickly added dropwise to 3.8 mL of concentrated hydrochloric acid to form a TiCl4 solution; the TiCl4 solution was added dropwise to the Ni(NO3)2 solution and stirred thoroughly at room temperature for 3 hours. 6.3594 g of Na2CO3 and 6.4 g of NaOH were weighed, dissolved with 200 mL of deionized water, dissolved at room temperature, and configured into an alkaline solution. The alkaline solution was then slowly added dropwise to the mixture of TiCl4 and Ni(NO3)2, stirring while adding until the pH of the solution was 9.5, to obtain a green suspension. The suspension was aged at 90°C for 24 hours. The obtained green precipitate was filtered, washed, and then dried at 60°C to obtain NiTi-LDH with a nickel-titanium ratio of 3. Its XRD spectrum is shown in detail. Figure 1 Curve a.

[0065] (2) Use a pipette to measure 3 mL of RuCl3 solution (Ru 3+ The concentration is 0.473 mg·mL -1 ). Take 0.2g NiTi-LDH support with a nickel-titanium ratio of 3 and place it in RuCl3 solution. After soaking for 20h at room temperature, dry it at 60℃ and then heat it at a space velocity of 7200mL·h -1 ·g -1 The Ru-Ni / NiTi-LDHs catalyst was obtained by reducing the Ru-Ni / NiTi-LDHs in a mixture of 50 vol.% H2 and 50 vol.% N2 at 350°C for 1.5 hours, wherein the nickel-titanium ratio was 3 and the Ru loading was 0.7 wt% of the mass of the NiTi-LDHs.

[0066] The performance of the catalyst was evaluated from Figure 5 It can be seen that the catalyst prepared in this example can reduce the CO outlet concentration to below 10 ppm at 180° C.-260° C. while maintaining a selectivity of more than 50%.

[0067] Example 5

[0068] (1) Add 8.724 g of Ni(NO3)2·6H2O to 100 mL of deionized water and dissolve it completely to obtain Ni(NO3)2 solution. In an ice-water bath, add 1.09 mL of 9.084 mol·L -1The TiCl4 was quickly added dropwise to 3.8 mL of concentrated hydrochloric acid to form a TiCl4 solution; the TiCl4 solution was added dropwise to the Ni(NO3)2 solution and stirred thoroughly at room temperature for 3 hours. 6.3594 g of Na2CO3 and 6.4 g of NaOH were weighed, dissolved with 200 mL of deionized water, dissolved at room temperature, and configured into an alkaline solution. The alkaline solution was then slowly added dropwise to the mixture of TiCl4 and Ni(NO3)2, stirring while adding until the pH of the solution was 9.5, to obtain a green suspension. The suspension was aged at 90°C for 24 hours. The obtained green precipitate was filtered, washed, and then dried at 60°C to obtain NiTi-LDH with a nickel-titanium ratio of 3. Its XRD spectrum is shown in detail. Figure 1 Curve a.

[0069] (2) Use a pipette to measure 3 mL of RuCl3 solution (Ru 3+ The concentration is 0.803 mg·mL -1 ). 0.2 g of NiTi-LDH support with a nickel-titanium ratio of 3 was placed in a RuCl3 solution, immersed for 20 h at room temperature, and then dried at 60 ° C. -1 ·g -1 The Ru-Ni / NiTi-LDHs catalyst was obtained by reducing the Ru-Ni / NiTi-LDHs in a mixture of 50 vol.% H2 and 50 vol.% N2 at 350°C for 1.5 h, wherein the nickel-titanium ratio was 3 and the Ru loading was 1.2 wt% of the mass of the NiTi-LDH.

[0070] The performance of the catalyst was evaluated from Figure 5 It can be seen that the catalyst prepared in this example can reduce the CO outlet concentration to below 10 ppm at 180° C.-260° C. while maintaining a selectivity of more than 50%.

[0071] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing a bimetallic catalyst for low-temperature selective methanation of CO, characterized in that The specific steps include: (1) Preparation of NiTi-LDH carrier by co-precipitation method: nickel salt is dissolved in water to obtain nickel salt solution (I); TiCl4 is mixed with concentrated hydrochloric acid to obtain a colorless or yellow clear solution (II); solution (II) is added to solution (I) to obtain a mixed solution (III); a mixed solution of NaOH and Na2CO3 (IV) is prepared as a precipitant; solution (IV) is added to solution (III), stirred evenly until complete precipitation occurs, the precipitate is aged, filtered, and dried to obtain a solid NiTi-LDH carrier; (2) taking the NiTi-LDH support obtained in step (1), impregnating it in a ruthenium salt solution, and then drying and reducing it to obtain a Ru-Ni / NiTi-LDH catalyst; Ni in step (1) 2+ With Ti 4+ The molar ratio is 2-3:1; The ruthenium salt in step (2) is ruthenium trichloride or ruthenium acetate; Ru in the ruthenium salt solution 3+ Concentration is 0.2-0.82 mg·mL -1 The Ru loading amount is 0.3wt%-1.2wt% of NiTi-LDH; the reduction temperature is 330-370℃; and the reduction time is 1-3 h.

2. The preparation method according to claim 1, wherein: The nickel salt in step (1) is one or more of nickel chloride, nickel nitrate, and nickel oxalate; Ni in the solution (I) of step (1) 2+ The concentration is 0.1-0.4 mol•L -1 .

3. The preparation method according to claim 1, wherein: The total concentration of metal cations in the mixed solution (III) in step (1) is 0.2-0.5 mol·L -1 .

4. The preparation method according to claim 1, wherein: Na in the precipitant of step (1) + The total concentration is 1.2-1.6 mol•L -1 , the molar ratio of Na2CO3 to NaOH is 0.3-0.5:1; The aging time in step (1) is 20-30 h, and the aging temperature is 80-95°C.

5. The preparation method according to claim 1, wherein: The immersion temperature in step (2) is room temperature and the immersion time is 12-24 h.

6. The preparation method according to claim 1, wherein: The reducing gas composition of step (2) is V N2 :V H2 =1:0.8-1.2:1; reducing gas space velocity is 6000-7200mL•h -1 •g -1 .

7. A bimetallic catalyst for low-temperature selective methanation of CO prepared by the method according to any one of claims 1 to 6.

8. Use of the bimetallic catalyst for low-temperature selective methanation of CO according to claim 7 for deep removal of trace CO in hydrogen-rich gas, characterized in that: The CO concentration in the hydrogen-rich gas is 0.5-1 vol.%; The reaction temperature of the catalyst when removing trace CO is 180°C-260°C.

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