A high-temperature stable catalyst for CH4 oxidation and a preparation method thereof

Abstract

The application discloses a high-temperature stable catalyst for CH4 oxidation and a preparation method thereof, and belongs to the technical field of catalysts, and comprises the following steps: taking SiO2 nanospheres as a matrix, introducing transition metal Ni through an impregnation method to form a core-shell structure composite carrier SiO2-NiO with a thin layer of NiO uniformly covering the surface; and then loading Pd on the composite carrier SiO2-NiO through the impregnation method to obtain a supported Pd-based catalyst SiO2-NiO-Pd, namely the high-temperature stable catalyst. The catalyst can be used for high-temperature methane catalytic combustion reaction, and has excellent catalytic activity, and the methane conversion rate can reach 100%.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalysts, and particularly relates to a high-temperature stable catalyst for CH4 oxidation and a preparation method thereof. BACKGROUND

[0002] With the increasing demand for energy and the increasingly stringent environmental requirements, methane (CH4) as a clean and efficient energy source with abundant reserves has gradually become an important substitute for traditional fossil fuels. However, if methane is not completely combusted during combustion, it will produce various pollutants including carbon monoxide (CO), volatile organic compounds (VOCs) and fine particulate matter (PM2.5), etc., causing serious environmental problems. At the same time, incomplete combustion will reduce energy utilization efficiency and limit the further promotion of methane as a clean energy source. Therefore, developing a high-efficiency catalyst that can achieve complete oxidation of methane has become an important research direction in the current energy field.

[0003] Catalysts for methane oxidation are mainly divided into two categories, namely noble metal catalysts and non-noble metal catalysts. Studies have shown that noble metal palladium (Pd) catalysts are widely studied and applied due to their high activity in complete methane oxidation, but Pd nanoparticles are prone to sintering and aggregation under high-temperature conditions, which leads to reduced catalytic activity and shortened service life. Therefore, how to improve the high-temperature stability and recycling performance of Pd catalysts has become a technical problem to be solved. By reasonably designing the catalyst carrier, such as introducing porous structure, high specific surface area and introducing transition metal to form strong metal-support interaction (SMSI) with Pd particles, the anti-sintering ability and activity of the catalyst can be significantly improved. Therefore, developing a new type of composite carrier based on SiO2 nanospheres combined with transition metal nickel (Ni) provides a new research direction and technical path for improving the performance of Pd-based methane catalysts.

[0004] Among the many factors that affect the performance of methane catalytic combustion, the size of the noble metal particles is considered one of the most important factors. Generally, the particle size affects the dispersion of the noble metal on the support, its valence state, and coordination number, which in turn affects the reaction. Among them, the silica (SiO2) support has become one of the hotspots in the study of Pd-based catalysts due to its unique structure and surface properties. The surface hydroxyl groups of SiO2 can interact with Pd nanoparticles, enhancing their dispersion and stability. This interaction not only prevents particle aggregation but also improves the mechanical strength of the catalyst. In the paper (Enhanced Thermal Stability of Palladium Catalysts on Mesoporous Silica for Methane Combustion.), the authors pointed out that mesoporous SiO2 support can significantly improve the thermal stability of Pd nanoparticles and methane catalytic performance. Its unique mesoporous structure allows rapid mass transfer of reactants and products within the pores, thus improving the overall reaction efficiency. However, mesoporous SiO2 may collapse at high temperatures (> 800℃), leading to a significant decrease in specific surface area, further causing Pd aggregation and deactivation. At the same time, due to the inertness of SiO2 in the oxidation environment, it lacks oxygen vacancies and cannot provide additional redox capacity for Pd, resulting in a decrease in Pd active sites and a decrease in catalytic activity. In addition, in the paper (Systematic Identification of Promoters for Methane Oxidation Catalysts Using Size and Composition Controlled Pd-Based Bimetallic Nanocrystals), the authors introduced a series of transition metals (M = V, Mn, Fe, Co, Ni, Zn, Sn) on the Al2O3 support and investigated their effects on the performance of methane catalytic oxidation. The study found that the Pd-Ni / Al2O3 catalyst had the largest increase in PdO decomposition temperature. This effect indicates that due to the strong interaction between Pd and NiO, NiO enhances the thermal stability of the PdO active phase, significantly improving the overall thermal stability and sintering resistance of the catalyst. However, the acidity of Al2O3 may cause Pd and NiO particles to agglomerate at high temperatures, reducing the activity of the catalyst. SUMMARY

[0005] Based on the above research background, the application provides a high-temperature stable catalyst for CH4 oxidation and a preparation method thereof.

[0006] To achieve the above object, the application provides the following technical scheme.

[0007] One of the objects of the application is to provide a preparation method of a high-temperature stable catalyst, comprising the following steps.

[0008] SiO2 nanospheres are used as a matrix, transition metal Ni is introduced by an impregnation method to form a core-shell structure composite carrier SiO2-NiO with a uniform thin layer of NiO on the surface; then Pd is loaded on the composite carrier SiO2-NiO by an impregnation method to obtain a supported Pd-based catalyst SiO2-NiO-Pd, i.e. a high-temperature stable catalyst.

[0009] The inertness of SiO2 material can ensure its stability at high working temperatures, and SiO2 has strong metal-support interaction (SMSI) and can become a suitable catalyst carrier. The application introduces transition metal nickel by an impregnation method to prepare a SiO2-NiO composite carrier. Ni oxide promotes the thermal stability of the catalyst by increasing the thermal stability of the active PdO phase, and effectively prevents the sintering and deactivation of Pd particles at high temperatures through strong metal-support interaction (SMSI) between Ni and Pd. Then Pd nanoparticles are loaded on the SiO2-NiO composite carrier by an impregnation method to form a SiO2-NiO-Pd high-temperature stable catalyst. The uniform NiO layer on the surface of the SiO2-NiO carrier provides ideal anchoring sites for the loading of Pd nanoparticles, significantly improving the catalytic activity and stability of Pd.

[0010] Further, the SiO2 nanospheres are prepared by a sol-gel method. The preparation steps include: mixing ammonia water with a concentration of 25-28wt%, anhydrous ethanol and deionized water, stirring, then adding tetraethyl orthosilicate, continuing to stir, centrifuging, drying to obtain SiO2 nanospheres;

[0011] The volume ratio of the ammonia water with a concentration of 25-28wt%, the anhydrous ethanol, the deionized water and the tetraethyl orthosilicate is (200-250):(200-250):(10-20):(20-30).

[0012] Further, the specific preparation steps of the composite carrier SiO2-NiO include: mixing SiO2 nanospheres with deionized water, adding a nickel source, adjusting pH to 6-7, and stirring until water evaporates to obtain the composite carrier SiO2-NiO.

[0013] The use amount ratio of the SiO2 nanospheres and the deionized water is (100-110) g: 250 mL.

[0014] The mass ratio of the SiO2 nanospheres and the nickel source is (100-110):(10-11), and the nickel source is nickel acetate.

[0015] Further, the SiO2-NiO-Pd includes fresh SiO2-NiO-Pd-F and aged SiO2-NiO-Pd-A.

[0016] The SiO2-NiO-Pd high-temperature stable catalyst doped with NiO can effectively reduce the methane light-off temperature.

[0017] Further, the specific preparation steps of the fresh SiO2-NiO-Pd-F include: mixing the composite carrier SiO2-NiO with deionized water, stirring, adding a palladium source, adjusting pH to 5-6, stirring until water evaporates, drying, calcining at a first temperature, and obtaining the fresh SiO2-NiO-Pd-F.

[0018] The specific preparation steps of the aged SiO2-NiO-Pd-A include: continuing to calcine the fresh SiO2-NiO-Pd-F at a second temperature to obtain the aged SiO2-NiO-Pd-A; and the second temperature is 180-320℃ higher than the first temperature.

[0019] Further, the addition amount of the palladium source is 1% of the mass of the composite carrier SiO2-NiO; and / or

[0020] The drying condition is: drying at 120℃ for 12h; and / or

[0021] The calcination condition is: calcining at 550-570℃ for 3h; and / or

[0022] The continued calcination condition is: calcining at 850-870℃ for 25h.

[0023] The second object of the present application is to provide a high-temperature stable catalyst prepared by the above preparation method. The obtained catalyst exhibits excellent high-temperature stability and methane catalytic oxidation performance.

[0024] The third purpose of the present application is to provide an application of the high-temperature stable catalyst in the CH4 complete oxidation reaction, which can be widely applied in the high-efficiency catalytic system in the clean energy field, especially suitable for long-time high-temperature operation environment, and provides a new catalyst design scheme for low-carbon energy transformation, and has a wide industrial application prospect.

[0025] The fourth purpose of the present application is to provide an application of the high-temperature stable catalyst in the high-efficiency catalytic system in the clean energy field.

[0026] Compared with the prior art, the present application has the following advantages and technical effects:

[0027] The present application successfully develops a catalyst with high catalytic activity and high-temperature thermal stability. The catalyst described in the present application not only meets the actual needs of clean energy utilization and low-carbon transformation, but also provides a new idea for improving the thermal stability of Pd catalyst in the methane catalytic combustion reaction.

[0028] The SiO2-doped Ni-supported palladium catalyst for methane catalytic combustion prepared by the present application can be used for high-temperature methane catalytic combustion reaction and has excellent catalytic activity, and the methane conversion rate can reach 100%. The catalyst shows excellent stability in the continuous combustion reaction process, that is, after 5 times of continuous use, it can still maintain 100% catalytic effect.

[0029] The catalyst prepared by the present application has a simple preparation process and can be used for a long time, and has a good practical application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0030] The accompanying drawings, which form a part of the present application, are used to provide a further understanding of the present application, and the schematic embodiments of the present application and their descriptions are used to explain the present application, and do not constitute an improper limitation on the present application. In the drawings:

[0031] Figure 1 The performance comparison chart of different catalysts in Example 1 and Comparative Example 1 under the condition of 40000 mL·min -1 ·g -1 gas flow rate;

[0032] Figure 2 The performance comparison chart of different catalysts in Example 1 and Comparative Example 1 under the condition of 40000 mL·min -1 ·g -1 , 60000 mL·min -1 ·g -1 , 80000 mL·min -1 ·g -1 gas flow rate;

[0033] Figure 3 The SiO2-NiO-Pd catalyst prepared in Example 1 was tested for 5 times under the same conditions of 40000 mL·min -1 ·g -1 The performance chart of the reaction of the SiO2-NiO-Pd catalyst prepared in Example 1 was tested for 5 times under the same conditions of 40000 mL·min

[0034] Figure 4 The TEM and EDX charts of the SiO2-NiO-Pd catalyst; wherein (a) is the TEM and EDX charts of the SiO2-NiO-Pd-F catalyst; and (b) is the TEM and EDX charts of the SiO2-NiO-Pd-A catalyst;

[0035] Figure 5 The TEM and EDX charts of the SiO2-Pd catalyst; wherein (a) is the TEM and EDX charts of the SiO2-Pd-F catalyst; and (b) is the TEM and EDX charts of the SiO2-Pd-A catalyst;

[0036] Figure 6 The XRD charts of different catalysts in Example 1 and Comparative Example 1; wherein a is the SiO2-Pd catalyst; and b is the SiO2-NiO-Pd catalyst;

[0037] Figure 7 The thermogravimetric curve of the SiO2-NiO-Pd catalyst prepared in Example 1; wherein a is the SiO2-NiO-Pd-F catalyst; and b is the SiO2-NiO-Pd-A catalyst;

[0038] Figure 8 The thermogravimetric curve of the SiO2-Pd catalyst prepared in Comparative Example 1; wherein a is the SiO2-Pd-F catalyst; and b is the SiO2-Pd-A catalyst;

[0039] Figure 9 The performance comparison chart of different catalysts in Example 1 and Comparative Example 2 under the same conditions of 40000 mL·min -1 ·g -1 The performance comparison chart of different catalysts in Example 1 and Comparative Example 2 under the same conditions of 40000 mL·min

[0040] Figure 10 The performance comparison chart of different catalysts in Example 1 and Comparative Example 2 under the same conditions of 40000 mL·min -1 ·g -1 , 60000 mL·min -1 ·g -1 , 80000 mL·min -1 ·g -1 ;

[0041] Figure 11are TEM and EDX images of a NiSiO3-Pd catalyst; where (a) is a TEM and EDX image of a NiSiO3-Pd-F catalyst; where (b) is a TEM and EDX image of a NiSiO3-Pd-A catalyst;

[0042] Figure 12 are XRD patterns of different catalysts in Example 1 and Comparative Example 2; where a is a SiO2-NiO-Pd catalyst; b is a NiSiO3-Pd catalyst;

[0043] Figure 13 are thermogravimetric curves of a NiSiO3-Pd catalyst prepared in Comparative Example 2; where a is a NiSiO3-Pd-F catalyst; b is a NiSiO3-Pd-A catalyst. DETAILED DESCRIPTION

[0044] Various illustrative embodiments of the present application are now described in detail below. The description made herein is not to be considered limiting, but rather as illustrative of certain aspects, features and embodiments of the present application.

[0045] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. Additionally, the use of the term "about" in relation to a value or a range of values is intended to include each individual intermediate value and each smaller range that falls within the range of values. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0046] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned herein are incorporated by reference to disclose and describe in full the methods and / or materials which are described therein. In the case of conflict between the present specification and any document incorporated herein by reference, the present specification will control.

[0047] Various modifications and changes can be made to the specific embodiments of the present application described herein without departing from the scope or spirit of the application. Other embodiments of the application will be apparent to those of ordinary skill in the art from the description and examples presented herein. The description and examples are illustrative of the application and are not intended to limit the scope of the application.

[0048] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", "contains", "containing", and the like are open-ended terms that are intended to mean including, but not limited to.

[0049] The application provides a high-temperature stable catalyst, which comprises a SiO2 carrier, Pd supported on the carrier, and doped transition metal Ni, and the main method comprises the following steps: S1, synthesizing a required SiO2 matrix by a method under the condition that ammonia water (25-28wt%) is used as an alkaline catalyst and deionized water and anhydrous ethanol are used as solvents; S2, loading Ni on the SiO2 matrix by a conventional impregnation method by adding a nickel acetate solution as a Ni precursor to the SiO2 matrix, and evaporating and drying the solution until water is evaporated, so as to obtain a SiO2-NiO composite carrier; S3, loading Pd on the SiO2-NiO carrier by a conventional impregnation method by adding a Pd(NO3)2 solution as a Pd precursor to the SiO2-NiO composite carrier, and evaporating and drying the solution until water is evaporated, so as to obtain a catalyst precursor SiO2-NiO-Pd loaded with Pd; S4, calcining the precursor SiO2-NiO-Pd in a muffle furnace to obtain a fresh catalyst (SiO2-NiO-Pd-F); and S5, continuing to calcine the SiO2-NiO-Pd-F in the muffle furnace to obtain an aged catalyst (SiO2-NiO-Pd-A). The application uses a stable SiO2 as a carrier, introduces an auxiliary agent Ni to improve the surface characteristics of the carrier, forms a SiO2-NiO composite carrier, and finally forms a SiO2-NiO-Pd catalyst.

[0050] The doped transition metal Ni can inhibit the decomposition of PdO particles, improve the thermal stability of an active phase, and thus improve the catalytic activity and thermal stability of the catalyst.

[0051] The specific technical scheme comprises the following steps:

[0052] (1) Preparation of SiO2 nanospheres: mixing ammonia water with a concentration of 25-28wt%, anhydrous ethanol and deionized water, stirring, then adding tetraethyl orthosilicate (TEOs), continuing to stir, centrifuging, and drying to obtain SiO2 nanospheres;

[0053] (2) Preparation of a composite carrier SiO2-NiO: mixing SiO2 nanospheres with deionized water, adding a nickel source, adjusting the pH to 6-7, stirring until water is evaporated, and drying to obtain a composite carrier SiO2-NiO;

[0054] (3) Preparation of fresh SiO2-NiO-Pd-F: the composite carrier SiO2-NiO is mixed with deionized water, stirred, a palladium source is added, and the pH is adjusted to 5-6, and after stirring until the water evaporates, drying, calcination, fresh SiO2-NiO-Pd-F is obtained;

[0055] (4) Preparation of aged SiO2-NiO-Pd-A: the composite carrier SiO2-NiO is mixed with deionized water, stirred, a palladium source is added, and the pH is adjusted to 5-6, and after stirring until the water evaporates, drying, calcination, fresh SiO2-NiO-Pd-F is obtained; the fresh SiO2-NiO-Pd-F is further calcined to obtain aged SiO2-NiO-Pd-A.

[0056] In some embodiments of the present application, the volume ratio of the 25-28wt% ammonia, anhydrous ethanol, deionized water and tetraethyl orthosilicate in step (1) is (200-250):(200-250):(10-20):(20-30). For example, in the following preferred embodiments of the present application, the volume ratio of the 25-28wt% ammonia, anhydrous ethanol, deionized water and tetraethyl orthosilicate is 245:225:10:21 or any range between the aforementioned ratios.

[0057] In some embodiments of the present application, the amount ratio of the SiO2 nanospheres and deionized water in step (2) is (100-110)g:250mL. For example, in the following preferred embodiments of the present application, the amount ratio of the SiO2 nanospheres and deionized water is 100g:250mL or any range between the aforementioned ratios.

[0058] In some embodiments of the present application, the mass ratio of the SiO2 nanospheres and nickel source in step (2) is (100-110):(10-11), and the nickel source is a 10wt% nickel acetate solution. For example, in the following preferred embodiments of the present application, the mass ratio of the SiO2 nanospheres and nickel source is 100:10 or any range between the aforementioned ratios.

[0059] In some embodiments of the present application, the temperature during stirring in step (2) is 70-80°C. For example, in the following preferred embodiments of the present application, the temperature during stirring is 70°C or any value between the aforementioned range. The drying temperature is 100-120°C. For example, in the following preferred embodiments of the present application, the drying temperature is 120°C or any value between the aforementioned range.

[0060] In some embodiments of the present application, the amount of the palladium source added in step (3) is 1wt% of the mass of the composite carrier SiO2-NiO, and the palladium source is a palladium nitrate solution with a mass concentration of 24wt%.

[0061] In some embodiments of the present application, the temperature during stirring in step (3) is 70-80℃; for example, in the following preferred embodiments of the present application, the temperature during stirring is 70℃ or any value between the aforementioned range.

[0062] In some embodiments of the present application, the temperature of calcination in step (3) is 550-570℃, and the calcination time is 3h. For example, in the following preferred embodiments of the present application, the temperature of calcination is 550℃ or any value between the aforementioned range.

[0063] In some embodiments of the present application, the temperature of continued calcination in step (4) is 850-870℃, and the time of continued calcination is 25h. For example, in the following preferred embodiments of the present application, the temperature of continued calcination is 850℃ or any value between the aforementioned range.

[0064] The high-temperature stable catalyst prepared by the above preparation method.

[0065] The application of the high-temperature stable catalyst in the CH4 complete oxidation reaction can be widely applied in high-efficiency catalytic systems in the field of clean energy, and is particularly suitable for long-time high-temperature operating environments, providing a new catalyst design scheme for low-carbon energy transformation and having a wide industrial application prospect.

[0066] The activity of the catalyst prepared in the present application is tested, and the reaction gas is a standard gas composed of CH4, O2 and N2, which is measured by a mass flow meter and a flow display instrument. The catalyst activity test is carried out in a quartz tube fixed bed reactor, the inner diameter of the quartz tube is 6mm, the length is 310mm, the catalyst is placed in the constant temperature zone of the reaction tube, the two sides are fixed with quartz wool, an electric furnace is used for heating, and a thermocouple is inserted into the furnace wall for temperature testing and control. The specific test method is as follows: after being pressed, ground and sieved, the catalyst particles with a size of 40-60 meshes are selected for activity evaluation. The test method is as follows: 0.5g of catalyst is loaded into a stainless steel reactor with an inner diameter of 5mm, the reaction gas is introduced to balance, and then the temperature is raised from 100℃ to 550℃ at a rate of 20℃ / min for catalyst pretreatment. After cooling to 100℃, the temperature is raised to 550℃ again for CH4 oxidation. The composition of the reaction gas is 5000ppm CH4, 6000ppm O2, and N2 as the balance gas, and the total gas flow rate is 40000-80000mL·min-1 ·g -1 The gas composition and content were detected on line by using the American Andover MKS multi-gas series FTIR gas analyzer.

[0067] The "room temperature" in the present application refers to 20-30℃ unless otherwise specified.

[0068] The raw materials used in the present application are commercially available.

[0069] The technical solutions of the present application are further illustrated by the following examples.

[0070] Example 1

[0071] A high-temperature stable catalyst, comprising the following steps:

[0072] (1) Preparation of SiO2 nanospheres: 245 mL of ammonia water was mixed with 225 mL of anhydrous ethanol and 10 mL of deionized water, stirred at room temperature for 30 min until the solution was uniformly mixed, then 21 mL of tetraethyl orthosilicate was added dropwise (dropping was completed within 2 min), stirred at room temperature for 4 h, the white product was separated by centrifugation, then transferred to a blast box and dried at 120℃ for 12 h to obtain SiO2 nanospheres;

[0073] (2) Preparation of composite carrier SiO2-NiO: 200 g of SiO2 nanospheres was dissolved in 500 mL of deionized water, and 20 g of 10 wt% nickel acetate solution was added when the SiO2 was completely dissolved without precipitation, and the pH was adjusted to 7 with ammonia water, and the solution was heated to 70℃ and stirred until the water evaporated, and the obtained material was placed in an oven and dried at 120℃ for 12 h to obtain the composite carrier SiO2-NiO;

[0074] (3) Preparation of fresh SiO2-NiO-Pd-F: 100 g of the composite carrier SiO2-NiO was dissolved in 500 mL of deionized water, and 0.42 g of 24 wt% palladium nitrate solution was added when the composite carrier SiO2-NiO was completely dissolved without precipitation, and the pH was adjusted to 6 with acetic acid and ammonia water, and the solution was heated to 70℃ and stirred until the water evaporated, and the obtained material was placed in an oven and dried at 120℃ for 12 h to obtain the SiO2-NiO-Pd catalyst precursor; the obtained SiO2-NiO-Pd catalyst precursor was calcined at 550℃ for 3 h in a muffle furnace to obtain fresh SiO2-NiO-Pd-F;

[0075] (4) Preparation of aged SiO2-NiO-Pd-A: the prepared fresh SiO2-NiO-Pd-F was further calcined at 850℃ for 25 h in a muffle furnace to obtain aged SiO2-NiO-Pd-A.

[0076] Comparative Example 1

[0077] A high-temperature stable catalyst, comprising the following steps:

[0078] (1) Preparation of SiO2nanospheres: 245 mL of ammonia water was mixed with 225 mL of anhydrous ethanol and 10 mL of deionized water, stirred at room temperature for 30 min until the solution was uniformly mixed, then 21 mL of tetraethyl orthosilicate was added dropwise (dropping was completed within 2 min), stirred at room temperature for 4 h, the white product was separated by centrifugation, then transferred to a blast box and dried at 120℃ for 12 h to obtain SiO2nanospheres;

[0079] (2) Preparation of SiO2-Pd precursor: 100 g of SiO2nanospheres was dissolved in 500 mL of deionized water, and 0.42 g of 24wt% palladium nitrate solution was added when the SiO2was completely dissolved without precipitation, the pH was adjusted to 6 with acetic acid and ammonia water, the solution was heated to 70℃ and stirred until the water in the solution evaporated, and the obtained material was placed in an oven and dried at 120℃ for 12 h to obtain SiO2-Pd precursor;

[0080] (3) Preparation of SiO2-Pd-F: the SiO2-Pd precursor was calcined at 550℃ for 3 h in a muffle furnace to obtain a fresh SiO2-Pd-F catalyst;

[0081] (4) Preparation of aged SiO2-Pd-A: the fresh SiO2-Pd-F catalyst prepared was further calcined at 850℃ for 25 h in a muffle furnace to obtain an aged SiO2-Pd-A catalyst.

[0082] Application Example 1

[0083] 1. Effect of catalyst on methane conversion

[0084] 0.5 g of the catalyst prepared in Example 1 and Comparative Example 1, respectively, was placed in the constant temperature zone of a fixed bed reactor quartz tube, fixed with quartz wool on both sides, and an electric furnace was heated. The reaction gas was introduced according to the above-mentioned method, and the specific composition was: 5000 ppm CH4, 6000 ppm O2, N2 as balance gas, and the total gas flow rate was 40000 mL·min -1 ·g -1 . The reaction temperature range was controlled at 100-550℃. The gas composition and content were detected online by American Andover MKS multi-gas series FTIR gas analyzer. The CH4conversion rate X can be calculated by formula (1):

[0085]

[0086] Figure 1 The CH4conversion rates of different catalysts in Example 1 and Comparative Example 1 at a gas flow rate of 40000 mL·min-1 ·g -1 (4W, same below) performance comparison chart under the same gas flow rate, the influence of different catalysts on methane conversion rate was investigated. The results showed that the highest methane conversion efficiency of SiO2-Pd-F catalyst was less than 80%, and the highest methane conversion efficiency of SiO2-Pd-A catalyst after aging treatment was even less than 50%. However, the methane conversion rate of SiO2-NiO-Pd-F catalyst doped with transition metal Ni could reach 100%, and the methane conversion rate of SiO2-NiO-Pd-A catalyst after aging treatment could still reach 98%. The reason is that nickel can be uniformly distributed on the surface of silicon dioxide, which can increase the interaction force with PdO active phase. At the same time, the presence of silicon dioxide helps to improve the stability of nickel, preventing nickel from agglomeration or loss during the reaction, which makes the catalyst still maintain good structure and catalytic performance under high temperature conditions of methane combustion.

[0087] 2, the influence of gas flow on the methane conversion rate of the catalyst

[0088] 0.5g of the catalyst prepared in Example 1 and Comparative Example 1 was respectively placed in the constant temperature zone of the fixed bed reactor quartz tube, fixed by quartz wool on both sides, and the electric furnace was heated. The reaction gas was introduced according to the above-mentioned method, and the specific composition was: 5000ppm CH4, 6000ppm O2, N2 as balance gas, and the total gas flow rate was 40000, 60000, 80000mL·min -1 ·g -1 respectively. The reaction temperature range was controlled at 100-550℃. The gas composition and content were detected online by American Andover MKS multi-gas series FTIR gas analyzer.

[0089] Figure 2 The performance comparison chart of different catalysts in Example 1 and Comparative Example 1 under the same conditions and different gas flow rates (40000mL·min -1 ·g -1 , 60000mL·min -1 ·g -1 , 80000mL·min -1 ·g -1 ) was investigated, and the influence of different gas flow on the methane conversion rate of the catalyst was investigated. The results showed that the gas flow rate had a greater influence on the performance of SiO2-Pd catalyst, and the light-off temperature increased with the increase of gas flow rate (40000mL·min -1 ·g -1 <60000mL·min -1 ·g -1 <80000mL·min -1 ·g -1). This indicates that as the gas flow rate increases, the contact time of methane with the catalyst surface is shortened, which is not conducive to the methane oxidation reaction at low temperature. The gas flow rate has little effect on the performance of the SiO2-NiO-Pd-F catalyst with strong catalytic activity. Although the light-off temperature also increases slightly with the increase of flow rate, the overall light-off temperature is significantly lower than that of the SiO2-Pd-F catalyst. The methane conversion rate of the SiO2-NiO-Pd-F catalyst at different gas flow rates of 40000 mL·min -1 ·g -1 , 60000 mL·min -1 ·g -1 , and 80000 mL·min -1 ·g -1 can reach 100%. This is because the uniform distribution of the NiO layer significantly enhances the activity and stability of Pd, and still maintains high catalytic performance at high flow rates. The results show that reasonable design of the catalyst carrier (introduction of NiO) can effectively improve the adaptability and performance stability of the catalyst at different gas flow rates, providing an important reference for the practical industrial application of methane catalytic oxidation.

[0090] 3. Catalyst for methane catalytic combustion cycle stability test

[0091] 0.5 g of the SiO2-NiO-Pd catalyst prepared in Example 1 was placed in the constant temperature zone of the fixed bed reactor quartz tube, fixed with quartz wool on both sides, and the electric furnace was heated. The reaction gas was introduced according to the above method, and the specific composition was: 5000 ppm CH4, 6000 ppm O2, N2 as balance gas, and the total gas flow rate was 40000 mL·min -1 ·g -1 . The reaction temperature range was controlled at 100-550°C. The American Andover MKS multi-gas series FTIR gas analyzer was used to detect the gas composition and content online. After completing the first round of testing, heating was stopped and it was allowed to cool naturally to room temperature. After the temperature was stable, a new round of catalytic activity evaluation was carried out under the same conditions as the first test to ensure the consistency and comparability of the subsequent tests, and the cycle was 5 times to determine the stability of the catalyst.

[0092] Figure 3 The SiO2-NiO-Pd catalyst prepared in Example 1 was tested at a gas flow rate of 40000 mL·min -1 ·g -1The performance of the reaction was tested for 5 cycles, and the cyclic stability of the SiO2-NiO-Pd catalyst for catalytic combustion of methane was investigated. The results showed that under the test conditions, the catalyst needs to withstand high-temperature oxidation, and the performance remains consistent after 5 cycles, indicating that the structural stability of the SiO2-NiO support and the dispersion of Pd particles are not damaged. The SiO2-NiO-Pd catalyst can achieve 100% methane conversion under the condition of a total gas flow rate of 40000 mL·min -1 ·g -1 In the 5-cycle test under the condition of a total gas flow rate of 40000 mL·min

[0093] 4. Catalyst structure and stability characterization

[0094] 1) The SiO2-NiO-Pd catalyst prepared in Example 1 was characterized, Figure 4 The TEM and EDX images of the SiO2-NiO-Pd catalyst showed that the SiO2 support in the fresh SiO2-NiO-Pd-F catalyst still had a complete spherical structure and a smooth surface, providing good support for Pd and NiO. The NiO and Pd on the surface of the SiO2 support were uniformly distributed, and there was no significant aggregation of particles. The spherical structure of the SiO2 support in the aged SiO2-NiO-Pd-A catalyst remained intact, but the surface may have been slightly rough or collapsed due to high temperature. High-temperature calcination caused partial reconstruction of the NiO layer, weakening its anchoring effect on Pd particles. Pd particles sintered under long-term high-temperature conditions, showing obvious agglomeration, resulting in uneven distribution of Pd.

[0095] 2) The SiO2-Pd catalyst prepared in Comparative Example 1 was characterized, Figure 5For the TEM and EDX images of SiO2-Pd catalysts, it can be seen that the spherical structure of SiO2 support in fresh SiO2-Pd-F catalyst is complete, and the surface is smooth without obvious deformation or cracks. Pd nanoparticles with small particle size are attached to the surface of SiO2, showing a uniform and dispersed state, and no obvious agglomeration phenomenon is observed, and the active sites are fully exposed. The influence of calcination at a lower temperature of 550 ℃ on the support and active components is small, which is beneficial to maintain the high dispersity and surface activity of Pd particles. The spherical structure of SiO2 support in aged SiO2-Pd-A catalyst is complete, but the surface is rough, which may be due to partial shrinkage or morphological change caused by high temperature. High-temperature and long-time calcination causes sintering of Pd particles to form large particles, reduces the dispersity, and leads to a decrease in specific surface area and a significant decrease in active sites. The roughening of the support surface and the migration of Pd caused by high-temperature and long-time calcination affect the overall performance of the catalyst, especially the catalytic efficiency in long-time high-temperature reaction.

[0096] 3) The SiO2-NiO-Pd catalyst prepared in Example 1 and the SiO2-Pd catalyst prepared in Comparative Example 1 were characterized. Figure a is the XRD curve of the SiO2-Pd catalyst, and the SiO2-Pd-F catalyst is treated at 550 ℃ for 3 h. The Pd(111) diffraction peak is weak and wide, indicating that the size of Pd nanoparticles is small (corresponding to the particle size distribution). SiO2 shows amorphous characteristics (wide background peak), indicating that the support has not been crystallized after being treated at 550 ℃ for 3 h. The Pd(111) diffraction peak of the SiO2-Pd-A catalyst is significantly enhanced and narrowed, indicating that the size of Pd particles is significantly increased. The amorphous characteristics of SiO2 remain unchanged, indicating that the support has good thermal stability, but the anchoring effect on Pd is weakened. Figure b is the XRD curve of the SiO2-NiO-Pd catalyst. The PdO crystal diffraction peak of the SiO2-NiO-Pd-F catalyst is weak, indicating that the crystallization degree of Pd particles is low, and the particles are small and have good dispersity. The Pd diffraction peak of the SiO2-NiO-Pd-A catalyst is significantly enhanced after being treated at 850 ℃ for 3 h, and the peak position is slightly shifted, which may be related to the increase in Pd particle size and the release of surface stress. The NiO diffraction peak is still clear in the aged state, which indicates that NiO has good thermal stability at high temperature, and may play a physical isolation and chemical anchoring role on Pd particles.

[0097] 4) The SiO2-NiO-Pd catalyst prepared in Example 1 was characterized, Figure 7The thermogravimetric curves (TGA) of the SiO2-NiO-Pd catalyst are shown. It can be seen that both the black curve (representing the mass change of the SiO2-NiO-Pd catalyst with temperature / time during programmed heating, hereinafter the same) and the red curve (representing the rate of mass change of the SiO2-NiO-Pd catalyst with temperature / time, with its peak point indicating the temperature / time point of the fastest rate of mass change in each sample, hereinafter the same) show no significant fluctuations, indicating very small mass loss (from room temperature to 1000℃, the remaining catalyst mass is close to 100%, with a mass change rate of less than 2%), demonstrating that the catalyst does not experience significant mass loss fluctuations throughout the heating process. The SiO2-NiO-Pd catalyst exhibits excellent thermal stability under both fresh and aged heat treatment conditions.

[0098] 5) The SiO2-Pd catalyst prepared in Comparative Example 1 was characterized. Figure 8 The thermogravimetric curves (TGA) of the SiO2-Pd catalyst prepared in Comparative Example 1 are shown. It can be seen that neither the black nor the red curves show significant fluctuations, indicating that the catalyst does not experience significant mass loss fluctuations throughout the heating process. The SiO2-Pd catalyst exhibits excellent thermal stability under heating conditions.

[0099] The results above demonstrate that this invention successfully prepared a Ni-doped SiO2-NiO-Pd catalyst via an impregnation method. A series of characterization analyses confirmed that the introduction of NiO into the uniform NiO layer formed by SiO2 not only enhances the generation of reactive oxygen species through oxygen vacancies and further improves the dispersibility and reactivity of Pd through the metal-support interaction (SMSI) between Ni and Pd, but also anchors the Pd particles, preventing their migration and aggregation at high temperatures. Compared to the undoped SiO2-Pd catalyst, at a gas flow rate of 40000 mL·min... -1 ·g -1 At that time, the T of the SiO2-NiO-Pd catalyst 50 As the temperature decreased from 486℃ to 386℃, T 90 The temperature was also reduced to 434℃. Cyclic test results showed that the SiO2-NiO-Pd catalyst could still maintain a high catalytic activity after 5 consecutive cycles.

[0100] Comparative Example 2

[0101] Same as Example 1, except that the preparation method of adding Ni to the composite support in step (2) is different, forming hollow NiSiO3 nanospheres. The specific technical solution is as follows:

[0102] A hollow NiSiO3 nanosphere supported catalyst includes the following steps:

[0103] (1) Preparation of SiO2 nanospheres: 245 mL of ammonia water was mixed with 225 mL of anhydrous ethanol and 10 mL of deionized water, stirred at room temperature for 30 min until the solution was uniformly mixed, then 21 mL of tetraethyl orthosilicate was added dropwise (dropping was completed within 2 min), stirred at room temperature for 4 h, the white product was separated by centrifugation, then transferred to a blast box and dried at 120°C for 12 h to obtain SiO2 nanospheres;

[0104] (2) Preparation of hollow NiSiO3 nanospheres: nickel acetate was dissolved in 160 mL of deionized water containing 0.8 g of SiO2 sol particles (nickel acetate was added according to a molar ratio of Si to Ni = 1:2, i.e. 6.63 g of nickel acetate), and the resulting mixture was ultrasonically irradiated for 60 min to form a uniform solution (the temperature was controlled in the range of 20-30°C), the obtained uniform solution was transferred to a stainless steel autoclave, which was sealed and kept at 180°C for 24 h, then air-cooled to room temperature to collect the obtained precipitate, washed with distilled water, and dried at 120°C for 12 h to obtain the hollow NiSiO3 carrier;

[0105] (3) Preparation of fresh NiSiO3-Pd-F: 100 g of the hollow NiSiO3 carrier was dissolved in 500 mL of deionized water until the carrier NiSiO3 was completely dissolved without precipitation, 0.42 g of 24wt% palladium nitrate solution was added, the pH was adjusted to 6 with acetic acid and ammonia water, the solution was heated to 70°C and continuously stirred until the water in the solution evaporated, and the obtained material was placed in an oven and dried at 120°C for 12 h to obtain the NiSiO3-Pd catalyst precursor;

[0106] (4) Preparation of fresh NiSiO3-Pd-F: the obtained NiSiO3-Pd catalyst precursor was calcined at 550°C for 3 h in a muffle furnace to obtain fresh NiSiO3-Pd-F;

[0107] (5) Preparation of aged NiSiO3-Pd-A: the prepared fresh NiSiO3-Pd-F was further calcined at 850°C for 25 h in a muffle furnace to obtain aged NiSiO3-Pd-A.

[0108] Application Example 2

[0109] 1. Effect of catalyst on methane conversion rate

[0110] 0.5g of the catalysts prepared in Example 1 and Comparative Example 2 were placed in the constant temperature zone of the quartz tube in the fixed-bed reactor, fixed on both sides with quartz wool, and heated by an electric furnace. The reaction gas was introduced as described above, with the specific composition being: 5000ppm CH4, 6000ppm O2, with N2 as the balance gas, and a total gas flow rate of 40000mL·min⁻¹·g⁻¹. The reaction temperature range was controlled between 100-550℃. The gas composition and content were detected online using an Andover MKS multi-gas series FTIR gas analyzer. The CH4 conversion rate X can be calculated using formula (1):

[0111]

[0112] Figure 9 The different catalysts used in Example 1 and Comparative Example 2 were tested at 40000 mL·min⁻¹·g. -1 (The image is abbreviated as 4W, the same below) This is a performance comparison chart under the same gas flow rate conditions, examining the effect of different catalysts on methane conversion. The results show that the NiSiO3-Pd-F catalyst has the highest methane conversion efficiency of 96%, while the NiSiO3-Pd-A catalyst after aging treatment has the highest methane conversion efficiency of 82%. (Comparison) Figure 1 The conversion rates of the NiSiO3-Pd-F catalyst were found to be close to those of the SiO2-Pd-F catalyst, but the curve was slightly flatter. This indicates that while the NiSiO3 support improved the dispersion of Pd, the surface lamellar structure limited gas diffusion during the reaction, resulting in a slightly lower overall reaction rate. The performance of the NiSiO3-Pd-A catalyst decreased, but remained higher than that of SiO2-Pd-A, especially under high-temperature aging (850℃ / 25 hours), where the surface needle-like structure effectively inhibited Pd agglomeration. This demonstrates that the NiSiO3 support plays a crucial role in maintaining the thermal stability and activity of Pd. The SiO2-NiO-Pd-F catalyst achieved a methane conversion rate of 100%, while the aged SiO2-NiO-Pd-A catalyst still maintained a methane conversion rate of 98%. The high conversion rate and very steep curve (fast conversion rate) of the SiO2-NiO-Pd-F catalyst indicate that the method of introducing NiO significantly affects the activity of Pd. The interfacial interaction between NiO and Pd enhances the number of catalytic active sites and optimizes the gas diffusion pathway. The SiO2-NiO-Pd-A catalyst exhibits optimal high-temperature stability, T 50 and T 90 The slight increase indicates that it maintains high activity even at high temperatures, suggesting a close correlation with the good anchoring of Pd particles. The variation in catalyst performance due to different Ni addition methods is because, in the SiO2-NiO-Pd catalyst prepared by the impregnation method, Ni mainly exists in the forms of NiO and NiO2, exhibiting obvious NiO diffraction peaks (e.g., XRD).Figure 12 ). The NiSiO3 hollow structure composite phase was generated by hydrothermal method. The formation of this morphology is because of the reaction between Ni and SiO2 to generate nickel silicate (NiSiO3) under hydrothermal conditions. XRD Figure 12 indicates that Ni mainly exists in the form of nickel silicate. In the impregnation method, Ni is attached to the surface of SiO2 in the form of direct deposition, without undergoing significant crystal reorganization and structural evolution, so Ni mainly exhibits oxidation state units, and the morphology of Ni plays an important role in the performance of the catalyst. NiO can be uniformly distributed on the surface of SiO2, which can increase the interaction force with PdO active phase. At the same time, the presence of SiO2 helps to improve the stability of nickel, preventing Ni from agglomeration or loss during the reaction, which makes the SiO2-NiO-Pd catalyst still maintain good structure and catalytic performance under high temperature conditions of methane combustion.

[0113] 2. Effect of gas flow rate on methane conversion rate of the catalyst

[0114] 0.5 g of the catalyst prepared in Example 1 and Comparative Example 2, respectively, was placed in the constant temperature zone of the fixed bed reactor quartz tube, fixed with quartz wool on both sides, and the electric furnace was heated. The reaction gas was introduced according to the above-mentioned method, and the specific composition was: 5000 ppm CH4, 6000 ppm O2, N2 as balance gas, and the total gas flow rate was 40000, 60000, 80000 mL·min -1 ·g -1 respectively. The reaction temperature range was controlled at 100-550℃. The American Andover MKS multi-gas series FTIR gas analyzer was used to detect the gas composition and content online.

[0115] Figure 10 The performance comparison chart of different catalysts in Example 1 and Comparative Example 2 under the same conditions and different gas flow rates (40000 mL·min -1 ·g -1 , 60000 mL·min -1 ·g -1 , 80000 mL·min -1 ·g -1 ) was used to investigate the effect of different gas flow rates on the methane conversion rate of the catalyst. The results show that the gas flow rate has a greater effect on the performance of the NiSiO3-Pd catalyst, and the light-off temperature increases with the increase of the gas flow rate (40000 mL·min -1 ·g -1 <60000 mL·min -1 ·g -1 <80000 mL·min -1 ·g -1). This indicates that with the increase of gas flow rate, the contact time of methane with the catalyst surface is shortened, which is not conducive to the methane oxidation reaction at low temperature. The gas flow rate has little effect on the performance of SiO2-NiO-Pd-F catalyst with strong catalytic activity. Although the light-off temperature also increases slightly with the increase of flow rate, the overall light-off temperature is significantly lower than that of NiSiO3-Pd-F catalyst. The methane conversion rate of SiO2-NiO-Pd-F catalyst at different gas flow rates of 40000 mL·min -1 ·g -1 , 60000 mL·min -1 ·g -1 , 80000 mL·min -1 ·g -1 can reach 100%, which is due to the uniform distribution of NiO layer, which significantly enhances the activity and stability of Pd, and still maintains high catalytic performance at high flow rate. The dependence of NiSiO3-Pd-F catalyst on space velocity is not as good as that of NiO2-NiO-Pd-F catalyst, but it still has high conversion rate at low space velocity (4W), which shows that the NiSiO3 structure can provide enough active sites at longer residence time. 50 and T 90 increases slightly with the increase of space velocity, but the amplitude is small, especially at 6W and 8W conditions, the conversion rate remains almost unchanged, which shows that the sensitivity of the catalyst to space velocity change is lower than that of SiO2-Pd-F catalyst. The hollow sphere structure of NiSiO3 support provides a larger specific surface area, and the surface has flaky and needle-like structure, forming a stable physical barrier to inhibit the migration and sintering of Pd. The catalytic activity of NiSiO3-Pd series is slightly lower than that of SiO2-NiO-Pd series, but its inhibition effect on Pd sintering is still significant. The results show that reasonable design of catalyst carrier (introduction of Ni) can effectively improve the adaptability and high-temperature stability of the catalyst at different gas flow rates, which provides an important reference for the practical industrial application of methane catalytic oxidation.

[0116] 3. Characterization of catalyst structure and stability

[0117] 1) The NiSiO3-Pd catalyst prepared in Comparative Example 2 was characterized, Figure 11For the TEM and EDX images of the NiSiO3-Pd catalyst, it can be seen that the TEM results of the NiSiO3-Pd-F catalyst show that the hollow spherical structure remains intact, but the morphology of the hollow sphere shrinks slightly, but still maintains the complete hollow structure, and the surface morphology of NiO presents a flaky shape (compared with the carrier, the structure changes), and the flaky structure is formed due to surface diffusion. This flaky structure may be an intermediate state of NiO formed during the preliminary heat treatment (short time and low temperature) to reduce energy. The EDX results show that the Pd particles of the NiSiO3-Pd-F catalyst are uniformly dispersed, and the particle distribution is fine, indicating that the pore structure of the NiSiO3 hollow sphere effectively inhibits the aggregation of Pd particles at high temperature. The TEM image of the NiSiO3-Pd-A catalyst shows that the hollow sphere further shrinks, and the flaky structure is further converted into a needle-like structure. At a higher temperature, the surface energy of the NiO particles is further reduced, leading to intensified crystal growth and recrystallization, and the high temperature promotes the expansion of the crystal surface, and the grains grow preferentially in a specific direction, and the surface forms a needle-like or nanorod morphology, and the hollow structure further shrinks. The EDX results show that the Pd particles of the NiSiO3-Pd-A catalyst still maintain good dispersity, and no obvious particle sintering or aggregation phenomenon is observed. The high specific surface area and excellent surface structure of the NiSiO3-Pd catalyst are beneficial to the dispersion of Pd.

[0118] 2) The SiO2-NiO-Pd catalyst prepared in Example 1 and the NiSiO3-Pd catalyst prepared in Comparative Example 2 were characterized. Figure 12 In the XRD curve of the SiO2-NiO-Pd catalyst, the PdO crystal diffraction peak intensity of the SiO2-NiO-Pd-F catalyst is weak, indicating that the Pd particles have a low degree of crystallization, small particle size and good dispersity. The Pd diffraction peak of the SiO2-NiO-Pd-A catalyst is obviously enhanced, and is accompanied by a slight peak shift, which may be related to the increase in Pd particle size and surface stress release. The NiO diffraction peak is still clear in the aged state, which indicates that NiO has good thermal stability at high temperature, and may play a physical isolation and chemical anchoring role on the Pd particles. Figure 12b is the XRD curve of NiSiO3-Pd catalyst, NiSiO3 support takes SiO2 as a template, under hydrothermal reaction condition, Ni(OH)2 is uniformly deposited on the SiO2 template and gradually forms a hollow sphere structure. The NiSiO3-Pd-F catalyst is dehydrated and decomposed into NiO (PDF 89-7101) after heat treatment at 550°C / 3h. Dehydration is accompanied by lattice rearrangement, which leads to increased crystallinity, sharp and high-intensity NiO peaks, which indicates that the crystallinity of the NiO phase is high at this time. The NiO (PDF 78-0643) of the NiSiO3-Pd-A catalyst after heat treatment at 850°C / 3h still maintains a hexagonal structure. High temperature promotes the generation of oxygen vacancies, leading to increased lattice stress, grain rearrangement, surface defect generation and particle agglomeration, and the NiO peak intensity is weakened and widened, indicating that the crystal size is reduced and the crystallinity is reduced. However, the crystal structure of NiO (PDF 78-0643) has more crystal defects and oxygen vacancies than (PDF 89-7101), which may cause unfavorable changes in the electronic structure of the Pd active center. The stability of the lattice decreases, the intensity of SMSI weakens, and the catalytic performance of Pd is affected.

[0119] 3) The NiSiO3-Pd catalyst prepared in Comparative Example 2 was characterized, Figure 13 The TG curve of the NiSiO3-Pd catalyst can be seen. The black and red curves do not have obvious fluctuations, indicating that the catalyst does not have obvious mass loss fluctuations during the entire temperature rise process. The NiSiO3-Pd catalyst exhibits excellent thermal stability under heating conditions.

[0120] From the above results, it can be seen that the SiO2-NiO-Pd catalyst doped with transition metal Ni and the NiSiO3-Pd catalyst doped with transition metal Ni are successfully prepared by the impregnation method. The introduction of NiO not only enhances the generation of active oxygen species through oxygen vacancies, but also further improves the dispersion and reactivity of Pd through the metal-support interaction (SMSI) between Ni-Pd, and the NiO layer plays an anchoring role for Pd particles to prevent their migration and aggregation at high temperatures. Compared with the SiO2-Pd catalyst without doping Ni, the anchoring effect of Pd is enhanced by doping Ni metal, and the interface design of the support (hollow nickel silicate nanospheres) is optimized to prevent Pd aggregation. The element doping strategy of this study significantly improves the methane conversion rate. The prepared SiO2-NiO-Pd catalyst and NiSiO3-Pd catalyst have significantly improved high-temperature stability, catalytic activity and space velocity dependence.

[0121] The above merely describes the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for preparing a high-temperature stable catalyst in a CH4 complete oxidation reaction, characterized by, The method comprises the following steps: SiO2 nanospheres are used as a substrate, a transition metal Ni is introduced by an impregnation method to form a core-shell structure composite carrier SiO2-NiO with a thin layer of NiO uniformly covering the surface, and then Pd is loaded on the composite carrier SiO2-NiO by the impregnation method to obtain a supported Pd-based catalyst SiO2-NiO-Pd, i.e. a high-temperature stable catalyst; The temperature range of the CH4 complete oxidation reaction is 100-550 DEG C; The SiO2-NiO-Pd includes fresh SiO2-NiO-Pd-F and aged SiO2-NiO-Pd-A; The specific preparation steps of the fresh SiO2-NiO-Pd-F include: mixing the composite carrier SiO2-NiO with deionized water, stirring, adding a palladium source, adjusting the pH to 5-6, stirring until the water evaporates, drying, and calcining at a first temperature to obtain the fresh SiO2-NiO-Pd-F; the palladium source is added in an amount of 1% of the mass of the composite carrier SiO2-NiO; the drying condition is 100-120 DEG C for 12 hours; and the calcining condition at the first temperature is 550-570 DEG C for 3 hours; The specific preparation steps of the aged SiO2-NiO-Pd-A include: continuing to calcine the fresh SiO2-NiO-Pd-F at a second temperature to obtain the aged SiO2-NiO-Pd-A; the second temperature is 180-320 DEG C higher than the first temperature; and the continuing calcining condition at the second temperature is 850-870 DEG C for 25 hours.

2. The method of claim 1, wherein the high-temperature stable catalyst is prepared by the steps of: The specific preparation steps of the SiO2 nanospheres include: mixing ammonia, anhydrous ethanol and deionized water, stirring, adding tetraethyl orthosilicate, continuing to stir, centrifuging, and drying to obtain the SiO2 nanospheres; The volume ratio of the ammonia, the anhydrous ethanol, the deionized water and the tetraethyl orthosilicate is (200-250):(200-250):(10-20):(20-30).

3. The method of claim 1, wherein the high-temperature stable catalyst is prepared by the steps of: The specific preparation steps of the composite carrier SiO2-NiO include: mixing SiO2 nanospheres with deionized water, adding a nickel source, adjusting the pH to 6-7, and stirring until the water evaporates to obtain the composite carrier SiO2-NiO; The use amount ratio of the SiO2 nanospheres and the deionized water is (100-110) g:250 mL; The mass ratio of the SiO2 nanospheres and the nickel source is (100-110):(10-11), and the nickel source is nickel acetate.

4. A high-temperature stable catalyst prepared by the preparation method in any one of claims 1-3.

5. Application of the high-temperature stable catalyst in claim 4 in a CH4 complete oxidation reaction.

6. Application of the high-temperature stable catalyst in claim 4 in a high-efficiency catalytic system in the field of clean energy.

Images