Sulfur-tolerant noble metal catalyst for oxidation of methane in lean methane and method for preparing and using the same

Abstract

This invention belongs to the field of catalytic oxidation technology, specifically relating to a sulfur-resistant noble metal catalyst for the oxidation of lean methane, its preparation method, and its application. The sulfur-resistant noble metal catalyst for the oxidation of lean methane provided by this invention uses an Ir@Pt core-shell structure as the active component, TiO2 as the support, and adds Al2O3 as a sulfur-resistant sacrificial agent through physical mixing, thereby improving the catalyst's stability. The catalyst is prepared by first using epitaxial growth to prepare Ir@Pt nanoparticles with Ir as the core and Pt as the shell, uniformly loading them onto a TiO2 support, and then physically grinding and mixing the resulting Ir@Pt / TiO2 catalyst with the sacrificial agent Al2O3. The catalyst of this invention has the advantages of high activity and high stability, and also exhibits high sulfur resistance activity and high sulfur resistance stability. When applied to the complete oxidation of lean methane, it can be used continuously for 50 hours without significant deactivation, achieving excellent technical results.

Description

Technical Field

[0001] This invention belongs to the field of catalytic oxidation technology, specifically relating to a sulfur-resistant noble metal oxidation catalyst for methane depletion, its preparation method, and its application. Background Technology

[0002] Methane, a major component of natural gas and shale gas, boasts advantages such as high reserves, high calorific value, and low carbon emissions, making it a clean energy source. Currently, methane is increasingly replacing coal and oil in natural gas vehicles, fuel cells, and direct combustion. However, during methane utilization, trace amounts of unutilized methane escape into the atmosphere, contributing to a severe greenhouse effect. Research indicates that catalytic oxidation technology can convert methane into CO2, which has a 23-fold lower warming potential, significantly reducing its greenhouse effect.

[0003] Currently, noble metal catalysts have attracted widespread attention due to their excellent methane oxidation activity at low temperatures. However, trace amounts of sulfur-containing gases (H2S and SO2) are inevitably introduced during natural gas extraction and the use of natural gas vehicles, leading to the deactivation of noble metal catalysts. Therefore, it is crucial to find a catalyst with high sulfur resistance for the oxidation of lean methane. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, this invention proposes a sulfur-resistant noble metal catalyst for the oxidation of methane. This catalyst uses an Ir@Pt core-shell structure as the active component, TiO2 as the support, and Al2O3 as a sulfur-resistant sacrificial agent added in a physical mixing manner. It is used in the reaction of complete methane oxidation and has high activity and high sulfur resistance stability.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] The first aspect of the present invention provides a sulfur-resistant methane oxidation catalyst, the catalyst comprising a support, an active component supported on the support, and a sacrificial agent added by physical mixing; the active component is metal Ir@Pt core-shell structured nanoparticles, the support is TiO2, and the sacrificial agent is Al2O3.

[0007] Preferably, the mass ratio of the metal Ir@Pt core-shell structured nanoparticles to the carrier TiO2 is 0.01 to 0.04:1.

[0008] Preferably, the mass ratio of the support TiO2 to the sacrificial agent Al2O3 is 1:0.3 to 0.7.

[0009] The second aspect of this invention provides a method for preparing the sulfur-resistant, low-methane oxidation catalyst described in the first aspect, comprising the following steps:

[0010] S1. The core metal precursor H2IrCl6 and a precipitant were added to a solution containing the template agent CTAB. After standing and centrifugation, the core metal nanoparticles were obtained.

[0011] S2. Dissolve the core metal nanoparticles obtained in step S1 in water, then add the shell metal precursor H2PtCl6 and the reducing agent, mix well to obtain a suspension of Ir@Pt core-shell structured nanoparticles.

[0012] S3. Add TiO2 support to the Ir@Pt core-shell structured nanoparticle suspension of S2, evaporate the water and then calcine to obtain the Ir@Pt / TiO2 catalyst.

[0013] S4. The Ir@Pt / TiO2 catalyst of S3 is mixed and ground with the sacrificial agent Al2O3 and then calcined to obtain a sulfur-resistant methane oxidation catalyst.

[0014] This invention synthesizes Ir@Pt core-shell nanoparticles on a TiO2 support using an epitaxial growth method, achieving high activity for methane oxidation. Furthermore, the Al2O3 incorporated through physical grinding does not alter the catalytic performance of the active component, but acts as a sacrificial agent for SO2 adsorption, protecting the active component and thus significantly improving the catalyst's sulfur resistance.

[0015] Preferably, the mass ratio of active metal Ir to Pt is 0.3 to 3:1.

[0016] Preferably, the precipitant is NaBH4 and the reducing agent is ascorbic acid (AA).

[0017] Preferably, the solution containing the template agent CTAB is an ethylene glycol solution containing the template agent CTAB, with a concentration of 4-6 mmol / 20 mL.

[0018] Preferably, the calcination described in S3 and S4 is carried out in air at 400-700°C for 1-3 hours.

[0019] Preferably, S1 is prepared into a solution of 7-15 mmol·L before adding the core metal precursor H2IrCl6. -1 The volume ratio of the H2IrCl6 solution to the solution containing the template agent CTAB is 1:3-5.

[0020] The third aspect of the present invention provides the application of the sulfur-resistant methane oxidation catalyst described in the first aspect in the methane oxidation reaction.

[0021] Preferably, the lean methane oxidation reaction specifically involves: placing the sulfur-resistant lean methane oxidation catalyst described in the first aspect inside a quartz tube, introducing a 10% H2 / Ar mixed gas, and oxidizing at 10°C for 1 minute. -1The temperature was increased to 500℃ for pretreatment for 1 hour; after cooling to room temperature, the reaction gas was introduced, and the catalyst was heated from room temperature at a rate of 10℃ / min. -1 The temperature is increased to the reaction temperature at a controlled rate; the inlet gas volume ratio is: CH4 = 0.25%–1%, O2 = (5%–20%), N2 is the equilibrium gas, the catalyst dosage is 0.02–0.2 g, and the total space velocity reaches 30,000–600,000 mL·g. -1 ·h -1 The reaction temperature is 200–600℃ and the reaction pressure is 0.1 MPa.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] This invention discloses a sulfur-resistant noble metal catalyst for the oxidation of lean methane. The catalyst uses an Ir@Pt core-shell structure as the active component, TiO2 as the support, and Al2O3 as a sulfur-resistant sacrificial agent through physical mixing, thereby effectively improving the catalyst's sulfur resistance stability. The catalyst is prepared by first using epitaxial growth to prepare Ir@Pt nanoparticles with an Ir core and a Pt shell, uniformly loading them onto a TiO2 support, and then physically grinding and mixing the resulting Ir@Pt / TiO2 catalyst with the sacrificial agent Al2O3. The catalyst of this invention has the advantages of high activity and high stability, and exhibits high sulfur resistance activity and stability. When applied to the complete oxidation of lean methane, it can be used continuously for 50 hours without significant deactivation, achieving excellent technical results. Detailed Implementation

[0024] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0025] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0026] Example 1:

[0027] This embodiment provides a sulfur-resistant methane oxidation catalyst, which includes an active component, a support, and a sacrificial agent. The active component is Ir@Pt core-shell structured nanoparticles, the support is TiO2, and the sacrificial agent Al2O3 is incorporated through physical grinding.

[0028] The preparation method of the sulfur-resistant, low-methane oxidation catalyst includes the following steps:

[0029] (1) Add 5 mmol of cetyltrimethylammonium bromide to 20 mL of ethylene glycol solution and heat to 60 °C to completely dissolve the particulate matter;

[0030] (2) Add 5 mL of 10 mmol·L⁻¹ -1 A suspension was obtained by mixing iridium chlorohydride solution and 0.0567 g of sodium borohydride, allowing it to stand for 6 hours, and then... (The sentence is incomplete and requires more context to translate accurately.) -1 Centrifuge for 15 minutes to obtain Ir nanoparticles;

[0031] (3) Disperse Ir nanoparticles (2-10 nm) in 200 mL of deionized water, stir vigorously and add 10 mmol·L⁻¹ -1 A chloroplatinic acid aqueous solution was prepared to make the mass ratio of Ir to Pt 3:1.

[0032] (4) Add 5 mL of ascorbic acid aqueous solution dropwise to make the molar ratio of Pt to ascorbic acid 1:20. After stirring and mixing, Ir@Pt core-shell structured nanoparticle suspension is obtained.

[0033] (5) Add TiO2 support to the suspension of Ir@Pt core-shell structured nanoparticles, so that the mass ratio of active components (Ir and Pt) to support TiO2 is 0.02:1. After drying and evaporating the water at 80°C, calcine at 500°C in air for 2 hours to obtain Ir@Pt / TiO2 catalyst.

[0034] (6) The Ir@Pt / TiO2 catalyst and the sacrificial agent Al2O3 were ground to make the mass ratio of the support TiO2 to the sacrificial agent Al2O3 1:1. The resulting solid particles were then placed in air and calcined at 500°C for 2 hours to obtain a sulfur-resistant methane oxidation catalyst.

[0035] Example 2:

[0036] This embodiment provides a sulfur-resistant methane oxidation catalyst, which includes an active component, a support, and a sacrificial agent. The active component is Ir@Pt core-shell structured nanoparticles, the support is TiO2, and the sacrificial agent Al2O3 is incorporated through physical grinding.

[0037] The preparation method of the sulfur-resistant, low-methane oxidation catalyst includes the following steps:

[0038] (1) Add 5 mmol of cetyltrimethylammonium bromide to 20 mL of ethylene glycol solution and heat to 60 °C to completely dissolve the particulate matter;

[0039] (2) Add 5 mL of 10 mmol·L⁻¹ -1A suspension was obtained by mixing iridium chlorohydride solution and 0.0567 g of sodium borohydride, allowing it to stand for 6 hours, and then... (The sentence is incomplete and requires more context to translate accurately.) -1 Centrifuge for 15 minutes to obtain Ir nanoparticles;

[0040] (3) Disperse the Ir nanoparticles in 200 mL of deionized water, stir vigorously and add 10 mmol·L⁻¹ -1 A chloroplatinic acid aqueous solution was prepared to make the mass ratio of Ir to Pt 1:1.

[0041] (4) Add 5 mL of ascorbic acid aqueous solution dropwise to make the molar ratio of Pt to ascorbic acid 1:20. After stirring and mixing, Ir@Pt core-shell structured nanoparticle suspension is obtained.

[0042] (5) Add TiO2 support to the suspension of Ir@Pt core-shell structured nanoparticles, so that the mass ratio of active component to support TiO2 is 0.02:1. After drying and evaporating water at 80°C, calcine at 500°C in air for 2 hours to obtain Ir@Pt / TiO2 catalyst.

[0043] (6) The Ir@Pt / TiO2 catalyst and the sacrificial agent Al2O3 were ground to make the mass ratio of the support TiO2 to the sacrificial agent Al2O3 1:1. The resulting solid particles were then placed in air and calcined at 500°C for 2 hours to obtain a sulfur-resistant methane oxidation catalyst.

[0044] Example 3:

[0045] This embodiment provides a sulfur-resistant methane oxidation catalyst, which includes an active component, a support, and a sacrificial agent. The active component is Ir@Pt core-shell structured nanoparticles, the support is TiO2, and the sacrificial agent Al2O3 is incorporated through physical grinding.

[0046] The preparation method of the sulfur-resistant, low-methane oxidation catalyst includes the following steps:

[0047] (1) Add 5 mmol of cetyltrimethylammonium bromide to 20 mL of ethylene glycol solution and heat to 60 °C to completely dissolve the particulate matter;

[0048] (2) Add 5 mL of 10 mmol·L⁻¹ -1 A suspension was obtained by mixing iridium chlorohydride solution and 0.0567 g of sodium borohydride, allowing it to stand for 6 hours, and then... (The sentence is incomplete and requires more context to translate accurately.) -1 Centrifuge for 15 minutes to obtain Ir nanoparticles;

[0049] (3) Disperse the Ir nanoparticles in 200 mL of deionized water, stir vigorously and add 10 mmol·L⁻¹ -1A chloroplatinic acid aqueous solution was prepared to make the mass ratio of Ir to Pt 1:3;

[0050] (4) Add 5 mL of ascorbic acid aqueous solution dropwise to make the molar ratio of Pt to ascorbic acid 1:20. After stirring and mixing, Ir@Pt core-shell structured nanoparticle suspension is obtained.

[0051] (5) Add TiO2 support to the suspension of Ir@Pt core-shell structured nanoparticles, so that the mass ratio of active component to support TiO2 is 0.02:1. After drying and evaporating water at 80°C, calcine at 500°C in air for 2 hours to obtain Ir@Pt / TiO2 catalyst.

[0052] (6) The Ir@Pt / TiO2 catalyst and the sacrificial agent Al2O3 were ground to make the mass ratio of the support TiO2 to the sacrificial agent Al2O3 1:1. The resulting solid particles were then placed in air and calcined at 500°C for 2 hours to obtain a sulfur-resistant methane oxidation catalyst.

[0053] Comparative Example 1:

[0054] The difference between Comparative Example 1 and Example 1 is that the step (6) of adding sacrificial agent Al2O3 is omitted in Comparative Example 1, while the remaining steps are the same as in Example 1, to obtain the Ir@Pt / TiO2 catalyst.

[0055] Comparative Example 2:

[0056] The difference between Comparative Example 2 and Example 1 is that the step (6) of adding sacrificial agent Al2O3 is omitted in Comparative Example 2, and the TiO2 support in step (5) is replaced with an Al2O3 support. The rest is the same as in Example 1, and the Ir@Pt / Al2O3 catalyst is obtained.

[0057] Experimental Example: Methane Oxidation Performance Test

[0058] First, introduce 10% H2 / Ar to allow the catalyst to react at 10 °C / min from room temperature. -1 The temperature was increased to 500℃ at a heating rate and held for 1 hour. After cooling to room temperature, a reaction gas was introduced, and then the catalyst was introduced from room temperature at a rate of 10℃·min. -1 The temperature was increased to the reaction temperature at a controlled heating rate. The inlet gas volume ratio was: CH4 = 0.25%–1%, O2 = (5%–20%), N2 was the equilibrium gas, and some experiments contained 50 ppm or 10 ppm SO2. The total space velocity reached 30,000 mL·g. -1 ·h -1 Or 600,000 mL·g -1 ·h -1 The catalyst dosage was 0.2 g (corresponding to 30000 mL·g). -1 ·h -1) or 0.02g (corresponding to 600,000 mL·g) -1 ·h -1 The reaction temperature was 200–600 °C, and the reaction pressure was 0.1 MPa. The catalysts obtained in Examples 1-3 and Comparative Examples 1-2 were reacted at a rate of 30,000 mL·g. -1 ·h -1 The catalytic oxidation of lean methane was carried out at a space velocity (reactant gas CH4:O2:N2 = 1:20:79, with or without 50 ppm SO2), and the results are shown in Table 1. The catalysts obtained in Example 1 and Comparative Examples 1-2 were subjected to a 600,000 mL·g⁻¹ air velocity (reactant gas CH4:O2:N2 = 1:20:79, with or without 50 ppm SO2). -1 ·h -1 The catalytic oxidation of lean methane was carried out at a space velocity (CH4:O2:N2 = 0.25:5:94.75, with or without 10 ppm SO2) and the results are shown in Table 2.

[0059] As shown in Tables 1 and 2, the catalyst prepared by this invention exhibits both high activity and high sulfur resistance, achieving a total space velocity of 30000 mL·g⁻¹ at CH₄:O₂:N₂ = 1:20:79. -1 ·h -1 At 325℃, the methane conversion rate can reach 90%, and at 350℃, the methane conversion rate is close to 100%. Meanwhile, the catalyst prepared in this invention, at 500℃, with CH4:O2:N2 = 1:20:79, 50ppm SO2, and 30000mL·g... -1 ·h -1 When the reaction was carried out continuously for 50 h at a space velocity of 100000 mL·g, the catalyst activity did not decrease significantly. Furthermore, at 550 °C, CH4:O2:N2 = 0.25:5:94.75, 10 ppm SO2, and 600000 mL·g, the catalyst activity remained stable. -1 ·h -1 Even under extreme conditions, the catalyst activity can still be maintained above 80% after continuous reaction for 12 hours.

[0060] Table 1. Catalysts at a space velocity of 30000 mL·g -1 ·h -1 Table of activity and sulfur resistance

[0061]

[0062] Table 2 Catalyst at a space velocity of 600,000 mL·g -1 ·h -1 Table of activity and sulfur resistance

[0063]

[0064]

[0065] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A sulfur tolerant, methane-lean oxidation catalyst characterized by, The catalyst comprises a carrier, an active component supported on the carrier, and a sacrificial agent added in a physical mixing manner; the active component is a metal Ir@Pt core-shell structure nanoparticle, the carrier is TiO2, and the sacrificial agent is Al2O3.

2. The sulfur tolerant, methane lean oxidation catalyst of claim 1, wherein, The mass ratio of the metal Ir@Pt core-shell structure nanoparticle to the carrier TiO2 is 0.01-0.04:

1.

3. The sulfur tolerant, methane lean oxidation catalyst of claim 1, wherein, The mass ratio of the carrier TiO2 to the sacrificial agent Al2O3 is 1:0.3-0.

7.

4. Process for the production of a sulphur tolerant lean methane oxidation catalyst according to any one of claims 1 to 3, characterised in that, The method comprises the following steps: S1, adding a core metal precursor H2IrCl6 and a precipitant into a solution containing a template agent CTAB, and obtaining core metal nanoparticles after standing and centrifugation; S2, dissolving the core metal nanoparticles obtained in step S1 in water, adding a shell metal precursor H2PtCl6 and a reducing agent, and obtaining an Ir@Pt core-shell structure nanoparticle suspension after mixing; S3, adding the carrier TiO2 into the Ir@Pt core-shell structure nanoparticle suspension of S2, evaporating water, and obtaining an Ir@Pt / TiO2 catalyst after calcination; S4, mixing and grinding the Ir@Pt / TiO2 catalyst of S3 with the sacrificial agent Al2O3, and obtaining a sulfur-tolerant lean-methane oxidation catalyst after calcination.

5. The process for producing a sulfur-tolerant lean-methane oxidation catalyst according to claim 4, characterized by, The mass ratio of the active metal Ir to Pt is 0.3-3:

1.

6. The process for producing a sulfur-tolerant lean-methane oxidation catalyst according to claim 4, characterized by, The precipitant is NaBH4, and the reducing agent is ascorbic acid.

7. The method for producing a sulfur-tolerant lean-methane oxidation catalyst according to claim 4, characterized by, The solution containing the template agent CTAB is an ethylene glycol solution containing the template agent CTAB, and the concentration is 4-6 mmol / 20 mL.

8. The process for producing a sulfur-tolerant lean-methane oxidation catalyst according to claim 4, characterized by, The calcination in S3 and S4 is calcination in air at 400-700 ℃ for 1-3 h.

9. The method for producing a sulfur-tolerant lean-methane oxidation catalyst according to claim 4, characterized by, S1 Before adding the core metal precursor H2IrCl6, it is first prepared into a 7-15 mmol·L -1 H2IrCl6 solution with a volume ratio of 1:3-5 to the solution containing the template agent CTAB.

10. Application of the sulfur-tolerant lean-methane oxidation catalyst in any one of claims 1-3 in a lean-methane oxidation reaction.

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