Gadolinium oxide loaded nano-alloy catalyst as well as preparation method and application thereof

Abstract

The invention discloses a RuIr-Gd2O3 bimetallic catalyst, a preparation method thereof and application of the RuIr-Gd2O3 bimetallic catalyst in a reaction for preparing synthesis gas by catalyzing N2O methane oxide dry reforming. The RuIr-Gd2O3 bimetallic catalyst is prepared from a Gd2O3 carrier and a RuIr bimetallic nano-alloy loaded on the Gd2O3 carrier, and the RuIr-Gd2O3 bimetallic catalyst is prepared from the RuIr-Gd2O3 bimetallic nano-alloy. The preparation method comprises the following steps: mixing the Gd2O3 carrier with a solution containing a Ru precursor and an Ir precursor, carrying out a stirring reaction under ultraviolet irradiation, evaporating the solvent to dryness, drying, and roasting in a reducing atmosphere to obtain the RuIr-Gd2O3 bimetallic catalyst. According to the method, efficient activation of N2O, precise cracking of CH4 and selective oxidation of an intermediate are realized through oxygen species slow release, redox center separation and bimetal site coordination strategies, so that the catalyst has high conversion rate and high CO / H2 yield at low temperature, and shows huge potential of cooperatively utilizing greenhouse gases under mild conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalysts, in particular to a RuIr-Gd2O3 bimetallic catalyst, a preparation method thereof and an application thereof in the preparation of syngas by the synergistic dry reforming of nitrous oxide (N2O) and methane (CH4). BACKGROUND

[0002] N2O is the third largest greenhouse gas, with a greenhouse effect 273 times that of CO2, and an atmospheric lifetime of more than 110 years. More worrying, N2O is also the most important ozone-depleting substance known. High concentrations of N2O (up to 10%~40% by volume) are emitted during industrial processes (such as the synthesis of adipic acid and caprolactam), and need to be treated efficiently.

[0003] CH4 is the second largest greenhouse gas, with a greenhouse effect 28 times that of CO2, and is widely present in natural gas and shale gas, and is also present in large quantities in landfill gas and coal-bed gas, and has important carbon resource value.

[0004] At present, only controlling CO2 is not enough to cope with the severe environmental challenge, and the synergistic conversion of N2O and CH4 has become a potential path for carbon emission reduction and resource utilization, with good development prospects and promotion opportunities.

[0005] Syngas (CO+H2) is an important basic platform chemical, which can be further converted into fuels or high-value chemicals through Fischer-Tropsch synthesis. Dry reforming is the most typical technology for the preparation of syngas, and traditional CO2-driven methane dry reforming (CO2-DRM) is an important method for the preparation of syngas. This technology realizes the emission reduction of CH4-CO2, the two greenhouse gases, for example, the nickel-based catalysts of patent applications CN116393158A and CN118663263A, which provide a solution for low-carbon energy development, but often require high temperatures of more than 650℃, and have problems such as high energy consumption, poor reaction selectivity, and catalyst sintering and deactivation.

[0006] N2O-driven methane dry reforming (N2O-DRM) has been proposed, which is expected to prepare syngas at a lower temperature and simultaneously reduce two strong greenhouse gases. The design of N2O-DRM catalysts needs to meet the following requirements: promoting the activation of CH4 and N2O, and inhibiting excessive oxidation.

[0007] The regulation of oxygen affinity is considered to be a key factor affecting the reaction path and product selectivity. In previous Fe-ZSM-5 and Cu-ZSM-5 systems, the regulation of "single-atom oxygen" intermediates produced by N2O decomposition has been used to develop selective methane oxidation processes (Science, 373, 327-331 (2021)), but the conversion of reactants is low, making it difficult to apply and promote. SUMMARY

[0008] The design idea of the present application is to prepare a catalyst with high activity and high selectivity for N2O-DRM reaction to synthesize syngas, and to simplify the preparation process as much as possible to promote industrial application. With this goal, the present application designs and constructs a Gd2O3 supported RuIr bimetallic catalyst (RuIr-Gd2O3), which realizes high-efficiency N2O-DRM reaction at only 450℃. Rare earth gadolinium oxide has a unique oxygen species release capability, which can realize controlled active oxygen release and reduce side reactions. The Ru site can effectively activate N2O and obtain monatomic oxygen species, and the Ir site can effectively activate CH4 and act as an active hydrogen species reservoir to generate H2, thereby realizing efficient greenhouse gas co-conversion and realizing high activity and high selectivity of N2O-DRP reaction. The present application not only first demonstrates the excellent performance of the Gd2O3 multi-metallic catalyst system in thermal catalysis research, but also provides a new strategy for the resource utilization of non-CO2 greenhouse gases.

[0009] The specific technical solutions of the present application are as follows: In a first aspect, the present application provides a RuIr-Gd2O3 bimetallic catalyst, comprising a Gd2O3 carrier and a RuIr bimetallic nanalloy supported on the Gd2O3 carrier.

[0010] Preferably, in the RuIr-Gd2O3 bimetallic catalyst, the mass fraction of Ru is 0.05% to 2.0%, for example 0.15%, 0.25%, 0.35%, etc., and further 0.1% to 1.0%.

[0011] Preferably, in the RuIr-Gd2O3 bimetallic catalyst, the mass fraction of Ir is 0.05% to 2.0%, for example 0.15%, 0.25%, 0.35%, etc., and further 0.1% to 1.0%.

[0012] By adjusting the mass ratio of Ru and Ir, the conversion rate, CO yield and H2 yield of the RuIr-Gd2O3 bimetallic catalyst in the catalytic N2O oxidation of methane dry reforming to synthesize syngas can be further optimized. Preferably, in the RuIr-Gd2O3 bimetallic catalyst, the mass ratio of Ru to Ir is 0.1 to 10:1, for example 1:1, and further 0.5 to 2:1.

[0013] In a second aspect, the present application provides a preparation method of the RuIr-Gd2O3 bimetallic catalyst of the first aspect, comprising: mixing a Gd2O3 carrier with a solution containing a Ru precursor and an Ir precursor, then stirring and reacting under ultraviolet light irradiation, then evaporating the solvent, and then calcining under a reducing atmosphere to obtain the RuIr-Gd2O3 bimetallic catalyst.

[0014] By the above preparation method, the Ru and Ir species can be highly dispersed and firmly combined in the form of nano-alloy on the surface of the Gd2O3 carrier, realizing synergistic utilization of the noble metal.

[0015] In some preferred examples, the preparation method of the Gd2O3 carrier comprises: calcining gadolinium nitrate to obtain the Gd2O3 carrier. The Gd2O3 thus obtained has high crystallinity. Preferably, the calcination temperature is 600-1200℃, for example 800℃, etc. Preferably, the calcination time is 2-48 hours, for example 12 hours, etc.

[0016] Preferably, the mixing method of the Gd2O3 carrier and the solution containing the Ru precursor and the Ir precursor is stirring and ultrasonic dispersion.

[0017] The RuIr-Gd2O3 bimetallic catalyst is obtained by calcining the solution. The solvent is evaporated before calcination, which can avoid excessive agglomeration of RuIr to form large particles. Preferably, the evaporation of the solvent is carried out under stirring.

[0018] Preferably, the Ru precursor comprises a chloride of Ru, for example ruthenium chloride, etc.

[0019] Preferably, the Ir precursor comprises a chloride of Ir, for example chloroiridic acid, etc.

[0020] By ultraviolet irradiation, the Ru-Cl and Ir-Cl bonds can be broken to improve the loading efficiency of the RuIr bimetallic nano-alloy.

[0021] Preferably, the wavelength of the ultraviolet light is 200-300 nm. For example, the ultraviolet light is UV-C.

[0022] Preferably, the reducing atmosphere comprises a hydrogen atmosphere.

[0023] Preferably, the calcination temperature is 550-650℃, for example 600℃, etc.

[0024] Preferably, the calcination time is 2-4 hours, for example 3 hours, etc.

[0025] In a third aspect, the application provides the use of the RuIr-Gd2O3 bimetallic catalyst of the first aspect in catalyzing the reaction of N2O oxidizing methane dry reforming to synthesize gas.

[0026] Preferably, in the use of the third aspect, the reaction of N2O oxidizing methane dry reforming to synthesize gas is carried out in a normal pressure (0.1 MPa) fixed bed continuous flow reactor, and the reaction conditions include: reaction temperature 200-700℃ (for example 350℃, 400℃, 450℃, 500℃, etc.), space velocity 1000-100000 mL g cat-1 h -1 (eg 30000 mL g cat -1 h -1 eg 1:1 etc.

[0027] In a fourth aspect, the present application provides a method for catalyzing N2O oxidative methane dry reforming to produce syngas, comprising: using the RuIr-Gd2O3 bimetallic catalyst of the first aspect to catalyze N2O oxidative methane dry reforming to produce syngas.

[0028] Preferably, the method of the fourth aspect is performed in a fixed-bed continuous flow reactor at normal pressure (0.1 MPa), and the reaction conditions include: a reaction temperature of 200-700℃ (eg 350℃, 400℃, 450℃, 500℃, etc.), a space velocity of 1000-100000 mL g cat -1 h -1 (eg 30000 mL g cat -1 h -1 eg 1:1 etc.

[0029] The RuIr-Gd2O3 bimetallic catalyst of the present application utilizes the unique oxygen species slow-release effect of the gadolinium oxide carrier and the bimetallic synergistic activation of RuIr nanoscale alloy to achieve the synergistic conversion of N2O and CH4 at medium-low temperature conditions, and has high activity, high selectivity and excellent stability. In the catalysis of N2O oxidative methane dry reforming to produce syngas, the RuIr-Gd2O3 bimetallic catalyst of the present application can utilize the oxygen species slow-release effect of the Gd2O3 carrier to achieve selective oxidation. Specifically, the gadolinium oxide carrier can slow-release active oxygen species generated by N2O decomposition at Ru sites, avoiding excessive oxidation side reactions, while Ir sites effectively activate CH4 molecules to generate active hydrogen species as a hydrogen source to participate in the formation of syngas, thereby realizing the synergistic effect of oxidation centers and reduction centers.

[0030] Compared with the prior art, the present application has the following beneficial effects: The RuIr-Gd2O3 bimetallic catalyst of the present application can effectively improve the activity, selectivity and CO / H2 space-time yield of N2O-methane dry reforming to produce syngas, and has an optimal operating temperature of 450℃ and can withstand high temperatures of 600℃. At 0.1 MPa (normal pressure), 450℃, N2O:CH4 molar ratio = 1, 30000 mL g cat -1 h -1Under these conditions, a N2O conversion rate of 99.3% and a methane conversion rate of 51.2% can be achieved, yielding 129.4 mol kg⁻¹. cat -1 h -1 CO yield and 199.6 mol kg cat -1 h -1 The H2 yield remained stable after 100 hours of continuous reaction, demonstrating excellent stability and application potential.

[0031] This invention achieves efficient N2O activation, precise CH4 cleavage, and selective oxidation of intermediates through a strategy of slow release of oxygen species, separation of redox centers, and synergistic bimetallic site utilization. This enables the catalyst to exhibit both high conversion rate and high CO / H2 yield at low temperatures, demonstrating its great potential for synergistic utilization of greenhouse gases under mild conditions. Detailed Implementation

[0032] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0033] Unless otherwise specified, the operating methods in the following examples are generally performed under conventional conditions or as recommended by the manufacturer.

[0034] Example 1: The preparation steps for a catalyst that can be used for N2O-methane dry reforming are as follows: Specific preparation process: Highly crystalline Gd₂O₃ is obtained by direct high-temperature calcination of Gd(NO₃)₃·6H₂O at 800℃ for 12 hours, yielding a Gd₂O₃ support. Metric amounts of ruthenium chloride and chloroiridium acid solutions are added dropwise to 20 mL of deionized water using a pipette, and stirred at 600 rpm for 30 min. The Gd₂O₃ support is then added to the above solutions (Gd₂O₃ mass / solution volume = 1 g / 20 mL), stirred, and ultrasonically dispersed to obtain a suspension. The suspension is then subjected to UV-C (7.8 mW cm⁻¹). -2) under irradiation and stirred at room temperature for 8 h; then evaporated to dryness at 70°C in an oil bath until no water was observed on the surface, and dried in an oven at 80°C until no free water was observed. Finally, the obtained powder was reduced at 600°C under hydrogen atmosphere for 3 h to obtain a RuIr-Gd2O3 bimetallic catalyst, which comprises a Gd2O3 support and a RuIr bimetallic nanalloy supported on the Gd2O3 support, and the mass fraction of Ru in the RuIr-Gd2O3 bimetallic catalyst is 0.25% and the mass fraction of Ir is 0.25%. The calcined powder was crushed into 40-60 mesh by tablet press at a pressure of 10 MPa for performance evaluation. The obtained catalyst is recorded as RuIr-Gd2O3-1.

[0035] Evaluation of the catalyst: The catalyst was accurately weighed and loaded into the reaction tube of a fixed-bed continuous flow reactor, and the upper and lower layers of the catalyst were fixed with quartz wool. The reaction was carried out at 0.1 MPa. The reaction temperature was measured by a thermocouple placed in the middle of the reaction tube and controlled by a programmed temperature controller, and the reaction temperature was 450°C. The gas flow was controlled by a mass flow meter, and the space velocity was 30000 mL g cat -1 h -1 The volume concentration of N2O and CH4 in the inlet gas was 30%, and He was used as the carrier gas. The evaluation results of the catalyst of Example 1 are shown in Table 1.

[0036] Example 2: The difference from Example 1 is only that no chloroiridic acid is added, and the rest is the same. The obtained catalyst is recorded as Ru-Gd2O3, and the mass fraction of Ru in the Ru-Gd2O3 catalyst is 0.5%. The evaluation results of the catalyst are shown in Table 1.

[0037] Example 3: The difference from Example 1 is only that no ruthenium chloride is added, and the rest is the same. The obtained catalyst is recorded as Ir-Gd2O3, and the mass fraction of Ir in the Ir-Gd2O3 catalyst is 0.5%. The evaluation results of the catalyst are shown in Table 1.

[0038] Example 4: The difference from Example 1 is only that the mass fraction of Ir in the RuIr-Gd2O3 bimetallic catalyst is 0.15% and the mass fraction of Ru is 0.35%, and the rest is the same. The obtained catalyst is recorded as RuIr-Gd2O3-2, and the evaluation results of the catalyst are shown in Table 1.

[0039] Example 5: The difference from Example 1 is only that the mass fraction of Ir in the RuIr-Gd2O3 bimetallic catalyst is 0.35%, the mass fraction of Ru is 0.15%, and the rest is the same, and the obtained catalyst is recorded as RuIr-Gd2O3-3. The catalyst evaluation results are shown in Table 1.

[0040] Table 1 In addition, it should be understood that, after reading the above description of the present application, those skilled in the art can make various modifications or modifications to the present application, and these equivalent forms also fall within the scope defined by the claims attached hereto.

Claims

1. A RuIr-Gd2O3 bimetallic catalyst, characterized in that, The RuIr-Gd2O3 bimetallic catalyst comprises a Gd2O3 carrier and a RuIr bimetallic nano-alloy loaded on the Gd2O3 carrier. 2.The RuIr-Gd 2O 3 bimetallic catalyst of claim 1, wherein, In the RuIr-Gd2O3 bimetallic catalyst: The mass fraction of Ru is 0.05% to 2.0%, further 0.1% to 1.0%, for example, 0.25%, etc. The mass fraction of Ir is 0.05% to 2.0%, further 0.1% to 1.0%, for example, 0.25%, etc.

3. The RuIr-Gd2O3 bimetallic catalyst according to claim 1 or 2, characterized in that, In the RuIr-Gd2O3 bimetallic catalyst, the mass ratio of Ru to Ir is 0.1 to 10:1, further 0.5 to 2:1, for example, 1:1, etc.

4. The preparation method of the RuIr-Gd2O3 bimetallic catalyst according to any one of claims 1-3, characterized in that, The RuIr-Gd2O3 bimetallic catalyst is prepared by mixing a Gd2O3 carrier with a solution containing a Ru precursor and an Ir precursor, stirring and reacting under irradiation of ultraviolet light, then evaporating the solvent, and calcining the dried product in a reducing atmosphere. The Gd2O3 carrier is prepared by calcining gadolinium nitrate.

5. The method for preparing the RuIr-Gd2O3 bimetallic catalyst according to claim 4, characterized in that, The calcination temperature is 600 to 1200°C.

6. The method for preparing the RuIr-Gd2O3 bimetallic catalyst according to claim 5, characterized in that, The calcination time is 2 to 48 hours. The mixing mode of the Gd2O3 carrier and the solution containing the Ru precursor and the Ir precursor is stirring and ultrasonic dispersion.

7. The method for preparing the RuIr-Gd2O3 bimetallic catalyst according to claim 4, characterized in that, The evaporation of the solvent is performed under stirring. The Ru precursor comprises a chloride of Ru. The Ir precursor comprises a chloride of Ir. The wavelength of the ultraviolet light is 200 to 300 nm. The reducing atmosphere comprises a hydrogen atmosphere. The calcination temperature is 550 to 650°C. The calcination time is 2 to 4 hours.

8. Use of the RuIr-Gd2O3 bimetallic catalyst according to any one of claims 1 to 3 in catalyzing the reaction of N2O oxidation methane dry reforming to produce syngas. The RuIr-Gd2O3 bimetallic catalyst according to any one of claims 1 to 3 is used to catalyze the reaction of N2O oxidation methane dry reforming to produce syngas.

9. Use according to claim 8, characterized in that, The catalytic N2O oxidation methane dry reforming reaction for synthesizing gas was carried out in a normal pressure fixed bed continuous flow reactor, and the reaction conditions included: the reaction temperature was 200-700 DEG C, the space velocity was 1000-100000 mL g cat -1 h -1 , and the molar ratio of N2O to CH4 was 0.1-10:

1.

10. A method for catalytic oxidation of methane dry reforming with N20 to syngas, characterized in that, ​ ​

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