A monolithic catalytic material for low carbon alkane oxidation and a preparation method and application thereof

Abstract

The application discloses a kind of monolithic catalytic material for low carbon alkane oxidation and its preparation method and application, palladium source is dissolved in hydrochloric acid, then group VIII transition metal nitrate is added, after stirring clarification, cerium oxide carrier is added, and pH is adjusted to 9-9.5, after stirring, it is placed, and catalyst powder is obtained by calcination;Catalyst powder is loaded on the surface of metal aluminum fiber carrier by wet impregnation method to obtain monolithic catalytic material, the mass percentage content of palladium in monolithic catalyst is 0.5%-1.0%.The material has rich oxygen vacancy, and the palladium dispersion is higher, compared with unmodified pure palladium loaded catalyst, the monolithic catalyst of strong electron-donating transition metal modified palladium has better low carbon alkane oxidation performance, and shows excellent water resistance, CO resistance and stability, has renewability, low cost, provides guiding idea for designing preparation of high efficiency, low cost, low carbon alkane oxidation catalyst with industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation technology, specifically relating to a monolithic catalytic material for the oxidation of low-carbon alkanes, its preparation method, and its application. Background Technology

[0002] Environmental pollution has always been a major problem restricting sustainable economic development. Since the beginning of the 21st century, with the advent of the modern industrial era, while enjoying economic boom, a series of environmental problems have also arisen. Volatile organic compounds (VOCs) are one of the important air pollutants, mainly originating from fuel combustion, transportation, and industrial waste gases. Furthermore, VOCs easily cause serious secondary pollution, leading to environmental problems such as smog, ozone layer depletion, and photochemical smog. Most VOCs are toxic and even carcinogenic, seriously threatening human health. Therefore, the comprehensive prevention and control of VOC pollution is an urgent task. Propane is a major VOC, originating from byproducts of the petrochemical industry and vehicle exhaust emissions. Currently, methods for eliminating propane include chemical, physical, and biological methods, mainly including adsorption, combustion, condensation, absorption, membrane separation, and catalytic oxidation. Among these, catalytic oxidation has attracted widespread attention from researchers due to its strong controllability, fewer secondary pollutants produced, and low combustion temperature.

[0003] Catalysts are the core of catalytic oxidation technology. Noble metal catalysts, such as Pd, Pt, Rh, and Ru, possess a large number of outermost electrons, enabling them to effectively activate CH bonds. However, their high cost limits their large-scale application as the sole active component. Non-noble metals, such as transition metals Fe, Co, and Ni, possess unsaturated 3d orbitals and strong electron-gaining / losing capabilities, exhibiting good initial activity in reactions such as the activation of low-carbon alkanes. However, non-noble metal catalysts typically suffer from poor stability and are prone to aggregation during use. Summary of the Invention

[0004] To overcome the problems in the prior art, the purpose of this invention is to provide an integral catalytic material for the oxidation of low-carbon alkanes, its preparation method and application. This method combines an inexpensive transition metal with a noble metal catalyst with good stability, thereby improving the catalyst activity and stability while reducing the catalyst cost. Furthermore, by coating the catalyst onto relatively inexpensive aluminum fibers, a high-performance, low-cost catalytic material for the catalytic oxidation of low-carbon alkanes with good prospects for industrial application is obtained.

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

[0006] A method for preparing a monolithic catalytic material for the oxidation of low-carbon alkanes includes the following steps:

[0007] The palladium source was dissolved in hydrochloric acid, then a Group VIII transition metal nitrate was added. After stirring and clarifying, a cerium oxide support was added, the pH was adjusted to 9-9.5, stirred, allowed to stand, and then calcined to obtain the catalyst powder.

[0008] Catalyst powder was loaded onto the surface of a metallic aluminum fiber support by wet impregnation to obtain a monolithic catalytic material. The mass percentage of palladium in the monolithic catalyst was 0.5%-1.0%.

[0009] Furthermore, the molar ratio of palladium source to transition metal nitrate is 1:3 to 1:15, and the mass of palladium source is 0.82% to 2.07% of the mass of cerium oxide support.

[0010] Furthermore, the palladium source is palladium acetate or palladium chloride.

[0011] Furthermore, the hydrochloric acid mass concentration is 37%, and the molar ratio of palladium source to hydrochloric acid is 1:2.

[0012] Furthermore, the transition metal nitrates are cobalt nitrate, nickel nitrate, or molybdenum nitrate.

[0013] Furthermore, the roasting temperature is 480-520℃, and the time is 3-5 hours;

[0014] The temperature is increased from room temperature to 480-520℃ at a heating rate of 2-5℃ / min.

[0015] Furthermore, the aluminum fiber carrier is prepared by the following process: the aluminum mesh is pretreated with an alkaline solution, then treated with water vapor at 100-120℃ for 10-14 hours, and then calcined in air at 350-400℃ for 3-5 hours to obtain the aluminum fiber carrier.

[0016] Furthermore, the cerium oxide support is prepared by the following process: using glycine or citric acid as a complexing agent and cerium nitrate as a cerium source, the cerium oxide support is prepared by combustion.

[0017] Further, Ce(NO3)3·6H2O was dissolved in deionized water and stirred until clear. Glycine was added, stirred evenly, and heated until gel-like. The temperature was then raised to 350-380℃, and after the glycine was ignited, cerium oxide support was obtained.

[0018] A monolithic catalytic material for the oxidation of low-carbon alkanes, prepared according to the method described above, has a diameter of 40-50 μm.

[0019] Application of a monolithic catalytic material for the oxidation of low-carbon alkanes prepared by the method described above in the oxidation and elimination of low-carbon alkanes.

[0020] Furthermore, 300 mg of monolithic catalyst material (40-60 mesh) was placed in a quartz tube, and a reaction gas was introduced at a flow rate of 100 mL / min, with a reaction space velocity of 20000 mL / h / g. cat The reaction occurs at 200-400℃; the volume percentage of propane in the reaction gas is 0.1%, the volume percentage of O2 is 20%, and the remainder is N2.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] This invention employs Pd nanoclusters modified with Group VIII transition metals. The advantage lies in the fact that the outermost orbitals of these elements are unsaturated 3d orbitals, exhibiting strong electron gain and loss capabilities, which can effectively improve catalyst performance. By using strong electron-donating transition metal-modified palladium nanoclusters and adjusting the ratio of Pd to the transition metal, strong oxygen vacancies and metal redox properties are constructed, increasing electron cloud density and thus improving the catalyst's low-carbon alkane oxidation activity, as well as its water resistance, CO resistance, and stability. This invention utilizes inexpensive transition metal-modified Pd nanoclusters, achieving high-performance low-carbon alkane oxidation-elimination catalysts while controlling catalyst costs. Furthermore, the monolithic catalyst material shows promising prospects for industrial application.

[0023] Furthermore, the aluminum fibers are pretreated with an alkaline solution to remove surface impurities, and then steam-treated to obtain an aluminum fiber carrier with a uniform alumina layer.

[0024] Furthermore, the present invention uses the glycine combustion method to prepare cerium oxide support, which has the advantage that by instantaneously igniting glycine, a cerium oxide support with more irregular mesoporous structures can be obtained. Attached Figure Description

[0025] Figure 1 This is the X-ray diffraction pattern of the Pd-xCo / CeO2 catalyst of the present invention.

[0026] Figure 2 This is a diagram showing the propane catalytic oxidation activity of the Pd-xCo / CeO2 catalyst of the present invention.

[0027] Figure 3 The results show the stability, water resistance, and CO resistance of the Pd-xCo / CeO2 catalyst of this invention.

[0028] Figure 4 This is the Raman spectrum of the Pd-xCo / CeO2 catalyst of the present invention.

[0029] Figure 5 This is a microscopic morphology image of an untreated aluminum fiber carrier.

[0030] Figure 6 This is a microscopic morphology diagram of the Pd-10Co / CeO2 monolithic catalytic material of the present invention. Detailed Implementation

[0031] The embodiments and accompanying drawings will help to understand the present invention, but do not limit the scope of the invention.

[0032] To reduce catalyst costs while ensuring activity and stability, combining inexpensive, strong electron-donating transition metals with noble metals is a promising solution, with strong electron-donating transition metals showing particularly good performance. Monolithic catalysts, due to their parallel, non-intersecting macroscopic channels, effectively reduce gas mass transfer resistance during reactions and are widely used in catalytic environmental protection fields. Metal meshes possess strong mechanical stability, excellent thermal conductivity, and good mass transfer properties, making them ideal catalyst substrates with great potential in industrial catalyst applications. Based on these foundations, this invention stabilizes Pd nanoclusters with transition metals, then loads them onto an oxygen-rich cerium oxide support, and finally coats them onto treated aluminum fibers, resulting in a high-performance, monolithic catalytic material with promising industrial applications for the oxidation of low-carbon alkanes.

[0033] The preparation method of the monolithic catalytic material for the oxidation of low-carbon alkanes of the present invention is as follows:

[0034] Pretreatment of aluminum fibers: First, the burrs on the surface of the aluminum mesh are sanded away. The aluminum mesh is then cut into aluminum fiber sheets 8 cm long and 2 cm wide. The cut aluminum fibers are then rolled into cylinders with a diameter of approximately 9 mm to obtain aluminum mesh cylinders. The aluminum mesh cylinders are then pretreated by immersing them in a 0.5 mol / L NaOH aqueous solution to remove surface impurities and irregular aluminum oxide layers, followed by multiple washes with deionized water. The treated aluminum mesh is then placed in a tube furnace and treated with steam at 100-120℃ for 10-14 hours. Finally, the atmosphere is switched to air, and the tube furnace is heated to 350-400℃ for calcination for 3-5 hours. Through steam treatment, a dense hydroxyl layer is formed on the surface of the rubbed aluminum fibers. During subsequent calcination, the hydroxyl groups react with the surface Al fibers to form aluminum oxide. The resulting oxide layer is more uniform than that of the untreated carrier, with similar oxidation levels in different areas.

[0035] A cerium oxide (CeO2) support was prepared by combustion using glycine or citric acid as a complexing agent and cerium nitrate as a cerium source. The specific process was as follows: First, 20 mmol of Ce(NO3)3·6H2O was weighed and dissolved in 50 mL of deionized water. After stirring until clear, 40 mmol of glycine was added and stirring was continued for 2 hours. Then, the solution was transferred to an 80°C water bath and stirred until it became gel-like. The resulting gel was placed in a muffle furnace and heated from room temperature to 350-380°C at a heating rate of 5-10°C / min. After the glycine was ignited, a CeO2 support with irregular mesopores was obtained.

[0036] A monolithic catalytic material for the oxidation of low-carbon alkanes was prepared by sodium hydroxide deposition precipitation method, with a palladium content (mass content) of 0.5%-1.0% in the catalyst. The specific process is as follows: using palladium acetate or palladium chloride as the palladium source, palladium chloride or palladium acetate is first dissolved in a 37% hydrochloric acid aqueous solution (the molar ratio of palladium chloride (or palladium acetate) to hydrochloric acid is 1:2). Then, a transition metal nitrate is added, and after stirring and clarification, a cerium oxide support is added. Subsequently, sodium hydroxide solution (precipitant) is added dropwise to adjust the pH to 9-9.5. The mixture is stirred for 2-4 hours to load palladium and transition metal onto the cerium oxide (CeO2) support. After uniform loading, the mixture is allowed to stand for 2-4 hours to allow palladium and transition metal to deposit on the surface of the cerium oxide support. The mixture is then washed three times with deionized water, dried for 12 hours, and transferred to a muffle furnace. The temperature is increased from room temperature to 480-520℃ at a heating rate of 2-5℃ / min, and calcined for 3-5 hours to obtain catalyst powder. The catalyst powder is then impregnated onto the surface of a metal aluminum fiber support using a wet impregnation method and dried to obtain a monolithic catalyst with a diameter of 40-50 μm. The molar ratio of palladium source to transition metal nitrate is 1:3 to 1:15, and the palladium source accounts for 0.82% to 2.07% of the mass of CeO2 support.

[0037] Transition metal nitrates are cobalt nitrate, nickel nitrate, or molybdenum nitrate.

[0038] This invention employs Group VIII transition metals (Co, Ni, Mo) to modify Pd nanoclusters. The advantage lies in the fact that the outermost orbitals of these elements are unsaturated 3d orbitals, exhibiting strong electron gain and loss capabilities, which can effectively improve catalyst performance. By using strong electron-donating transition metals to modify palladium nanoclusters, and adjusting the ratio of Pd to the transition metal, strong oxygen vacancies and metal redox properties are constructed, increasing electron cloud density, thereby improving the catalyst's low-carbon alkane oxidation activity and stability.

[0039] The mass content of palladium oxide is 0.5%-1.0%, and the mass content of transition metal oxides is 3.0%-10.0%.

[0040] The monolithic catalyst prepared by the above method can be used in the oxidative elimination of low-carbon alkanes. Specifically, 300 mg of screened 40-60 mesh monolithic catalyst material is placed in a quartz tube, and a reaction gas is introduced at a flow rate of 100 mL / min, with a reaction space velocity of 20000 mL / h / g. cat The reaction occurs at 200-400℃; the volume percentage of propane in the reaction gas is 0.1%, the volume percentage of O2 is 20%, and the remainder is N2.

[0041] In this invention, the loading amount is a percentage by mass.

[0042] The CeO2 support and aluminum fiber support in Examples 1-4 were prepared through the following process:

[0043] Preparation of aluminum fiber carrier: First, the burrs on the surface of the aluminum mesh were removed by sanding. The aluminum mesh was then cut into aluminum fiber sheets 8 cm long and 2 cm wide. The cut aluminum fibers were then rolled into cylinders with a diameter of approximately 9 mm to obtain aluminum mesh cylinders. The aluminum mesh cylinders were then pretreated by immersing them in a 0.5 mol / L NaOH aqueous solution to remove surface impurities and irregular oxide layers, followed by repeated washing with deionized water. The treated aluminum mesh was then placed in a tube furnace and treated with steam at 120°C for 12 hours. Finally, the atmosphere was switched to air, and the tube furnace was heated to 400°C for calcination for 4 hours to obtain the aluminum fiber carrier.

[0044] Preparation of cerium oxide (CeO2) support: First, 20 mmol of Ce(NO3)3·6H2O was weighed and dissolved in 50 mL of deionized water. After stirring until clear, 40 mmol of glycine was added and stirring was continued for 2 hours. Then, the solution was transferred to an 80 °C water bath and stirred until gel-like. The resulting gel was placed in a muffle furnace and heated from room temperature to 350 °C at a heating rate of 5 °C / min. After the glycine was ignited, CeO2 support with irregular mesopores was obtained.

[0045] Example 1

[0046] First, weigh 0.0736 g of palladium acetate (Pd(OAC)₂)₂ and dissolve it in a 37% hydrochloric acid solution (molar ratio of Pd(OAC)₂:hydrochloric acid = 1:2). After stirring and clarifying, add 0.4351 g of Co(NO₃)₃. .After stirring and clarifying with 6H2O, 3.84g of CeO2 support was added. The mixture was stirred for 30 minutes, and then 2mol / L NaOH solution was added dropwise to adjust the pH to approximately 9-9.5. The mixture was stirred for 2 hours and then allowed to stand for 2 hours. The precipitate was then washed three times with deionized water and dried in an oven at 80℃ for 12 hours. It was then transferred to a muffle furnace and heated to 500℃ at a heating rate of 2℃ / min for 4 hours to obtain Pd-3Co / CeO2 catalyst powder. Finally, using a wet impregnation method with methanol as the solvent, the obtained Pd-3Co / CeO2 catalyst powder was impregnated onto the surface of an aluminum fiber support. After impregnation for 2 hours, it was dried in an oven at 80℃ to obtain a monolithic catalyst.

[0047] The loading of PdO was 1.0%, and the loading of Co3O4 was 3.0%.

[0048] Example 2

[0049] First, weigh 0.0736 g of palladium acetate (Pd(OAC)₂)₂ and dissolve it in a 37% hydrochloric acid solution (molar ratio of Pd(OAC)₂:hydrochloric acid = 1:2). After stirring and clarifying, add 0.8702 g of Co(NO₃)₂. . After stirring and clarifying with 6H2O, 3.72g of the prepared CeO2 support was added. The mixture was stirred for 30 minutes, and then 2mol / L NaOH solution was added dropwise to adjust the pH to approximately 9-9.5. The mixture was stirred for 4 hours and then allowed to stand for 3 hours. The precipitate was then washed three times with deionized water and dried in an oven at 80℃ for 12 hours. It was then transferred to a muffle furnace and heated to 500℃ at a heating rate of 2℃ / min for 4 hours to obtain the Pd-6Co / CeO2 catalyst. Finally, using a wet impregnation method with methanol as the solvent, the obtained Pd-6Co / CeO2 catalyst powder was impregnated onto the surface of a treated aluminum fiber support (i.e., aluminum mesh). After impregnation for 2 hours, it was dried in an oven at 80℃ to obtain the monolithic catalyst.

[0050] The loading of PdO was 1.0%, and the loading of Co3O4 was 6.0%.

[0051] The difference between Example 2 and Example 1 is the Co3O4 loading.

[0052] Example 3

[0053] First, weigh 0.0736 g of palladium acetate (Pd(OAC)₂)₂ and dissolve it in a 37% hydrochloric acid solution (molar ratio of Pd(OAC)₂:hydrochloric acid = 1:2). After stirring and clarifying, add 1.1603 g of Co(NO₃)₂. .After stirring and clarifying with 6H2O, 3.64g of the prepared CeO2 support was added. The mixture was stirred for 30 minutes, and then 2mol / L NaOH solution was added dropwise to adjust the pH to approximately 9-9.5. The mixture was stirred for 4 hours and then allowed to stand for 3 hours. The precipitate was then washed three times with deionized water and dried in an oven at 80℃ for 12 hours. It was then transferred to a muffle furnace and heated to 500℃ at a heating rate of 2℃ / min for 4 hours to obtain the Pd-8Co / CeO2 catalyst. Finally, using a wet impregnation method with methanol as the solvent, the obtained Pd-8Co / CeO2 catalyst powder was impregnated onto the surface of the treated aluminum fiber support. After impregnation for 2 hours, it was dried in an oven at 80℃ to obtain the monolithic catalyst.

[0054] The loading of PdO was 1.0%, and the loading of Co3O4 was 8.0%.

[0055] The difference between Example 3 and Examples 1 and 2 lies in the Co3O4 loading.

[0056] Example 4

[0057] First, weigh 0.0736 g of palladium acetate (Pd(OAC)₂)₂ and dissolve it in a 37% hydrochloric acid solution (molar ratio of Pd(OAC)₂:hydrochloric acid = 1:2). After stirring and clarifying, add 1.4503 g of Co(NO₃)₂. . After stirring and clarifying with 6H2O, 3.56g of the prepared CeO2 support was added. The mixture was stirred for 30 minutes, and then 2mol / L NaOH solution was added dropwise to adjust the pH to approximately 9-9.5. The mixture was stirred for 4 hours and allowed to stand for 2 hours. The precipitate was then washed three times with deionized water and dried in an oven at 80℃ for 12 hours. It was then transferred to a muffle furnace and heated to 500℃ at a heating rate of 2℃ / min for 4 hours to obtain the Pd-10Co / CeO2 catalyst. Finally, using a wet impregnation method with methanol as the solvent, the obtained Pd-10Co / CeO2 catalyst powder was impregnated onto the surface of the treated aluminum fiber support. After impregnation for 2 hours, it was dried in an oven at 80℃ to obtain the monolithic catalyst.

[0058] The loading of PdO was 1.0%, and the loading of Co3O4 was 10.0%.

[0059] The difference between Example 4 and Example 1, Example 2 and Example 3 is the amount of Co3O4 loading.

[0060] Comparative Example 1

[0061] First, 0.0736 g of palladium acetate (Pd(OAC)₂)₂ was dissolved in hydrochloric acid solution (Pd(OAC)₂: hydrochloric acid = 1:2). After stirring and clarifying, 3.92 g of the prepared CeO₂ support was added. After stirring for 30 minutes, 2 mol / L NaOH solution was added dropwise to adjust the pH to approximately 9-9.5. The mixture was stirred for 2 hours and then allowed to stand for 2 hours. The mixture was then washed three times with deionized water. The resulting precipitate was dried in an oven at 80°C for 12 hours, then transferred to a muffle furnace and heated to 500°C at a heating rate of 2°C / min for 4 hours to obtain the Pd / CeO₂ catalyst. Finally, using a wet impregnation method with methanol as the solvent, the catalyst powder obtained above was impregnated onto the surface of a treated aluminum mesh. After impregnation for 2 hours, the mesh was dried in an oven at 80°C to obtain the monolithic catalyst.

[0062] The PdO loading is 1.0%.

[0063] Example 5

[0064] Preparation of aluminum fiber carrier: First, the burrs on the surface of the aluminum mesh were removed by sanding. The aluminum mesh was then cut into aluminum fiber sheets 8 cm long and 2 cm wide. The cut aluminum fibers were then rolled into cylinders with a diameter of approximately 9 mm to obtain aluminum mesh cylinders. The aluminum mesh cylinders were then pretreated by immersing them in a 0.5 mol / L NaOH aqueous solution to remove surface impurities and irregular oxide layers, followed by repeated washing with deionized water. The treated aluminum mesh was then placed in a tube furnace and treated with steam at 100°C for 14 hours. Finally, the atmosphere was switched to air, and the tube furnace was heated to 370°C for calcination for 4 hours to obtain the aluminum fiber carrier.

[0065] Preparation of cerium oxide (CeO2) support: First, 20 mmol of Ce(NO3)3·6H2O was weighed and dissolved in 50 mL of deionized water. After stirring until clear, 40 mmol of glycine was added and stirring was continued for 2 hours. Then, the solution was transferred to an 80 °C water bath and stirred until gel-like. The resulting gel was placed in a muffle furnace and heated from room temperature to 380 °C at a heating rate of 10 °C / min. After the glycine was ignited, CeO2 support with irregular mesopores was obtained.

[0066] First, 0.0736 g of palladium chloride was dissolved in a 37% hydrochloric acid solution (molar ratio of palladium chloride to hydrochloric acid = 1:2). After stirring and clarifying, nickel nitrate was added, and after stirring and clarifying, CeO2 support was added. After stirring for 30 minutes, 2 mol / L NaOH solution was added dropwise to adjust the pH to 9. The mixture was stirred for 2 hours and then allowed to stand for 2 hours. The mixture was then washed three times with deionized water. The resulting precipitate was dried in an oven at 80℃ for 12 hours, then transferred to a muffle furnace and heated to 500℃ at a heating rate of 2℃ / min for 3.5 hours to obtain catalyst powder. Finally, the catalyst powder was impregnated onto the surface of an aluminum fiber support using methanol as a solvent via a wet impregnation method. After impregnation for 2 hours, the powder was dried in an oven at 80℃ to obtain a monolithic catalyst. The molar ratio of palladium chloride to nickel nitrate was 1:5, and the mass of palladium chloride was 0.82% of the mass of the CeO2 support.

[0067] The loading of PdO is 0.5%, and the loading of nickel oxide is 1.0%.

[0068] Example 6

[0069] Preparation of aluminum fiber carrier: First, the burrs on the surface of the aluminum mesh were removed by sanding. The aluminum mesh was then cut into aluminum fiber sheets 8 cm long and 2 cm wide. The cut aluminum fibers were then rolled into cylinders with a diameter of approximately 9 mm to obtain aluminum mesh cylinders. The aluminum mesh cylinders were then pretreated by immersing them in a 0.5 mol / L NaOH aqueous solution to remove surface impurities and irregular oxide layers, followed by repeated washing with deionized water. The treated aluminum mesh was then placed in a tube furnace and treated with steam at 110°C for 11 hours. Finally, the atmosphere was switched to air, and the tube furnace was heated to 350°C for calcination for 5 hours to obtain the aluminum fiber carrier.

[0070] Preparation of cerium oxide (CeO2) support: First, 20 mmol of Ce(NO3)3·6H2O was weighed and dissolved in 50 mL of deionized water. After stirring until clear, 40 mmol of glycine was added and stirring was continued for 2 hours. Then, the solution was transferred to an 80 °C water bath and stirred until gel-like. The resulting gel was placed in a muffle furnace and heated from room temperature to 360 °C at a heating rate of 7 °C / min. After the glycine was ignited, CeO2 support with irregular mesopores was obtained.

[0071] First, 0.0736 g of palladium chloride was dissolved in a 37% hydrochloric acid solution (molar ratio of palladium chloride to hydrochloric acid = 1:2). After stirring and clarifying, molybdenum nitrate was added, and after stirring and clarifying, CeO2 support was added. After stirring for 30 minutes, 2 mol / L NaOH solution was added dropwise to adjust the pH to 9. The mixture was stirred for 2 hours and then allowed to stand for 2 hours. The mixture was then washed three times with deionized water. The resulting precipitate was dried in an oven at 80°C for 12 hours, then transferred to a muffle furnace and heated to 520°C at a heating rate of 5°C / min for 3 hours to obtain catalyst powder. Finally, the catalyst powder was impregnated onto the surface of an aluminum fiber support using methanol as a solvent via a wet impregnation method. After impregnation for 2 hours, the powder was dried in an oven at 80°C to obtain a monolithic catalyst. The molar ratio of palladium chloride to molybdenum nitrate was 1:14.3, and the mass of palladium chloride was 1.148% of the mass of the CeO2 support.

[0072] The loading of PdO is 0.7%, and the loading of molybdenum oxide is 10%.

[0073] Example 7

[0074] Preparation of aluminum fiber carrier: First, the burrs on the surface of the aluminum mesh were removed by sanding. The aluminum mesh was then cut into aluminum fiber sheets 8 cm long and 2 cm wide. The cut aluminum fibers were then rolled into cylinders with a diameter of approximately 9 mm to obtain aluminum mesh cylinders. The aluminum mesh cylinders were then pretreated by immersing them in a 0.5 mol / L NaOH aqueous solution to remove surface impurities and irregular oxide layers, followed by repeated washing with deionized water. The treated aluminum mesh was then placed in a tube furnace and treated with steam at 120°C for 10 hours. Finally, the atmosphere was switched to air, and the tube furnace was heated to 350°C for calcination for 5 hours to obtain the aluminum fiber carrier.

[0075] Preparation of cerium oxide (CeO2) support: First, 20 mmol of Ce(NO3)3·6H2O was weighed and dissolved in 50 mL of deionized water. After stirring until clear, 40 mmol of citric acid was added and stirring was continued for 2 hours. Then, the solution was transferred to an 80 °C water bath and stirred until gel-like. The resulting gel was placed in a muffle furnace and heated from room temperature to 350 °C at a heating rate of 5 °C / min. After the citric acid was ignited, CeO2 support with irregular mesopores was obtained.

[0076] First, 0.0736 g of palladium acetate was dissolved in a 37% hydrochloric acid solution (molar ratio of palladium acetate to hydrochloric acid = 1:2). After stirring and clarifying, cobalt nitrate was added, and after stirring and clarifying, CeO2 support was added. After stirring for 30 minutes, 2 mol / L NaOH solution was added dropwise to adjust the pH to 9.5. The mixture was stirred for 2 hours and then allowed to stand for 2 hours. The mixture was then washed three times with deionized water. The resulting precipitate was dried in an oven at 80℃ for 12 hours, then transferred to a muffle furnace and heated to 480℃ at a heating rate of 3℃ / min for 5 hours to obtain catalyst powder. Finally, the catalyst powder was impregnated onto the surface of an aluminum fiber support using methanol as a solvent via a wet impregnation method. After impregnation for 2 hours, the powder was dried in an oven at 80℃ to obtain a monolithic catalyst. The molar ratio of palladium acetate to cobalt nitrate was 1:6.25, and the mass of palladium acetate was 1.6% of the mass of the CeO2 support.

[0077] The loading of PdO is 0.8%, and the loading of molybdenum oxide is 5%.

[0078] Example 8

[0079] The difference from Example 1 is that the molar ratio of palladium acetate to cobalt nitrate is 1:3.

[0080] Example 9

[0081] The difference from Example 1 is that the molar ratio of palladium acetate to cobalt nitrate is 1:15.

[0082] The propane oxidation activity tests in Examples 1, 2, 3, 4, and Comparative Example 1 were conducted in a fixed reaction bed. 300 mg of the monolithic catalyst was weighed and placed in a quartz tube, and a reaction gas of 1000 ppm C3H8 + 20% O2 / N2 (100 mL / min, GHSV = 20000 mL / h / g) was introduced. cat The test temperature range is 150-400℃, and the exhaust gas is detected by gas chromatography equipped with an FID detector.

[0083] X-ray diffraction and Raman spectroscopy were used to characterize Examples 1, 2, 3, 4 and Comparative Example 1 in various aspects.

[0084] The X-ray diffraction patterns of Examples 1, 2, 3, 4, and Comparative Example 1 are as follows: Figure 1As shown, the catalyst's crystal phase is predominantly CeO2. With increasing Co3O4 loading, characteristic diffraction peaks of Co3O4 appear in Pd-8Co / CeO2 and Pd-10Co / CeO2. Furthermore, no PdO species were observed, indicating that PdO species are highly dispersed on the CeO2 support surface. The dispersion of active metals is generally closely related to catalyst performance; higher dispersion is more beneficial to catalyst reactivity.

[0085] The propane oxidation activity diagrams for Examples 1, 2, 3, 4, and Comparative Example 1 are shown below. Figure 2 As shown, compared to the monolithic Pd / CeO2 catalyst of pure Pd, the catalysts modified with transition metals all exhibited better propane oxidation performance, and the catalyst activity gradually increased with increasing Co3O4 content. Among them, the propane conversion rate of the Pd-10Co / CeO2 catalyst reached 90% (T0). 90 The temperature was 220℃, while the T of the unmodified Pd / CeO2 catalyst was... 90 The temperature reached 340℃. Propane catalytic oxidation test results show that the performance of the catalyst can be significantly improved by modifying the Pd catalyst with transition metals.

[0086] The propane oxidation stability, water resistance, and CO resistance test results of Example 4 and Comparative Example 1 are as follows: Figure 3 As shown, select their respective T 90 The temperature used was the stability test temperature. The optimal catalysts Pd-10Co / CeO2 and the unmodified Pd / CeO2 catalyst from Example 4 and Comparative Example 1 were tested for stability, water resistance, and CO resistance at 220℃ and 340℃, respectively. According to the stability, water resistance, and CO resistance test results, the propane conversion rate of the Pd-10Co / CeO2 catalyst reached over 90% within the initial 30 minutes. After introducing 10% water vapor, the propane conversion rate did not decrease significantly. After stopping the water vapor introduction, the propane conversion rate recovered to over 90%. Subsequently, the introduction of 1000 ppm CO resulted in a slight decrease in propane conversion rate, but it was not significant. After removing the CO, the propane conversion rate recovered to over 90%, and there was no significant decrease after 40 hours of testing. In contrast, the propane conversion rate of the unmodified Pd / CeO2 catalyst consistently decreased, and its activity declined significantly after the introduction of 10% water vapor and CO. With increasing stability testing time, the propane conversion rate dropped from over 90% initially to below 80%. The results of the catalyst's stability, water resistance, and CO resistance tests indicate that Co modification can significantly enhance the catalyst's stability and resistance to water and CO.

[0087] For oxidative elimination reactions, the oxygen properties on the catalyst surface play a crucial role in the catalyst's stable oxidation performance. To further investigate the surface oxygen properties of the catalyst, Raman spectroscopy was performed on Examples 1, 2, 3, 4, and Comparative Example 1. The test results are as follows: Figure 4 As shown. 462cm -1 The peak at that location can be attributed to F on the CeO2 support. 2g Vibration, 600cm -1 The peak at 690 cm⁻¹ can be attributed to oxygen vacancies on the catalyst surface. -1 The peak at that point is due to the A of Co3O4 1g Vibration-induced. The oxygen vacancy concentration on the catalyst surface is expressed as I. Ov / I F2g With increasing Co3O4 content, the number of oxygen vacancies on the catalyst surface increases significantly. Raman spectroscopy results indicate that transition metal modification can effectively increase the number of oxygen vacancies in the catalyst, thus improving the propane oxidation reaction performance of the catalyst.

[0088] Figure 5 Microscopic morphology images of untreated aluminum fiber carriers, from Figure 5 As can be seen, the surface of the untreated aluminum fiber has many irregular burrs, which will affect the deposition of the load.

[0089] Figure 6 See the microstructure diagram of Example 4. Figure 6 It can be seen that the diameter of the aluminum fibers is approximately 40 μm, and a distinct layer of powder can be observed coating the surface of the aluminum fibers. Figure 5 Compared to untreated aluminum fiber carriers, there are no obvious burrs on the surface.

[0090] The catalytic material of this invention has abundant oxygen vacancies and high palladium dispersion. Compared with unmodified pure palladium supported catalysts, the monolithic catalyst modified with a strong electron-donating transition metal, palladium, exhibits superior low-carbon alkane oxidation performance, excellent water resistance, CO resistance, and stability. It is also regenerable and inexpensive, providing guidance for the design and preparation of efficient, low-cost low-carbon alkane oxidation catalysts with promising industrial applications.

Claims

1. A method for preparing a monolithic catalytic material for the oxidation of low-carbon alkanes, characterized in that, Includes the following steps: Palladium source was dissolved in hydrochloric acid, then a Group VIII transition metal nitrate was added. After stirring and clarifying, cerium oxide support was added, the pH was adjusted to 9-9.5, stirred, allowed to stand, and calcined to obtain catalyst powder. The molar ratio of palladium source to transition metal nitrate was 1:3-1:15, and the mass of palladium source was 0.82%-2.07% of the mass of cerium oxide support. Cerium oxide support was prepared by the following process: using glycine or citric acid as a complexing agent and cerium nitrate as a cerium source, cerium oxide support was prepared by combustion. Catalyst powder was loaded onto the surface of a metallic aluminum fiber support using a wet impregnation method to obtain a monolithic catalytic material. The mass percentage of palladium in the monolithic catalyst was 0.5%-1.0%. The metallic aluminum fiber support was prepared by the following process: pretreating the aluminum mesh with an alkaline solution, and then... o Treat with steam for 10-14 hours, then in air at 350-400°C. o After calcining at C for 3-5 hours, a metallic aluminum fiber carrier is obtained. The palladium source is palladium acetate or palladium chloride; the transition metal nitrate is cobalt nitrate, nickel nitrate or molybdenum nitrate; the calcination temperature is 480-520℃ and the time is 3-5h; the temperature is increased from room temperature to 480-520℃ at a heating rate of 2-5℃ / min.

2. The method for preparing the monolithic catalytic material for the oxidation of low-carbon alkanes according to claim 1, characterized in that, The hydrochloric acid mass concentration is 37%, and the molar ratio of palladium source to hydrochloric acid is 1:

2.

3. A monolithic catalytic material for the oxidation of low-carbon alkanes prepared according to the method of claim 1 or 2, characterized in that, The diameter of the catalyst material is 40-50 μm.

4. The application of a monolithic catalytic material for the oxidation of low-carbon alkanes prepared according to the method of claim 1 or 2 in the oxidation and elimination of low-carbon alkanes.

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