Nickel-loaded semiconductor oxide-based catalyst for methanation of carbon dioxide in photo-thermal catalytic flue gas as well as preparation method and application of nickel-loaded semiconductor oxide-based catalyst

Abstract

The invention discloses a nickel-loaded semiconductor oxide-based catalyst for methanation of carbon dioxide in photo-thermal catalytic flue gas as well as a preparation method and application of the nickel-loaded semiconductor oxide-based catalyst. The photo-thermal catalyst takes a semiconductor oxide as a carrier, and nickel metal is loaded through impregnation, calcination and reduction treatment. The Ni metal nanoparticles serve as carbon dioxide hydrogenation sites, the semiconductor oxide material stimulates oxygen in flue gas to be combined with reactants under light driving to generate more reactivity intermediates, and surface oxygen vacancies formed by the reduction treatment material further enhance the adsorption and activation capacity of the catalyst to the reactants. The preparation process is simple and the cost is low. In the reaction of methanation of carbon dioxide in photo-thermal catalytic flue gas, the catalyst shows high-efficiency activity, and the selectivity gt of methane in the product is realized; 99%. Besides, the method has the advantages of mild reaction conditions, simplicity and convenience in operation, environmental friendliness and the like, provides an efficient and feasible way for resource utilization of carbon dioxide, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of thermal and photothermal catalytic synthesis, specifically relating to a nickel-supported semiconductor oxide catalyst and its preparation method, as well as its application in the thermal, full-spectrum driven catalytic carbon dioxide methanation reaction in flue gas. Background Technology

[0002] With the deepening of global industrialization, the greenhouse effect caused by massive carbon dioxide emissions has become a major challenge facing human society. More than 65% of these carbon emissions originate from flue gas from furnaces and kilns in energy-intensive industries such as power generation, cement, and steel. Therefore, developing carbon utilization technologies for such flue gas is of great strategic significance for achieving carbon resource recycling and sustainable development. In-situ catalytic conversion of carbon dioxide near the emission source to directly synthesize high-value-added energy products or chemical raw materials is an ideal path to solving this problem. However, flue gas has a complex composition (containing nitrogen, oxygen, water vapor, carbon dioxide, etc.). According to existing reports, the presence of oxygen limits the activity of carbon dioxide methanation reactions and leads to an increase in CO byproducts, thus restricting its resource utilization.

[0003] In catalyst design, nickel-supported semiconductor oxides exhibit great potential in methanation reactions due to their excellent catalytic activity, high chemical stability, and low cost. Suitable semiconductor oxide supports can not only stably disperse nickel nanoparticles, but their own optical and electrical properties, in synergy with nickel, can also improve the separation efficiency of photogenerated carriers and enhance the overall utilization of photothermal energy by the catalyst. Combining photothermal catalysis technology with the synergistic use of light and heat energy can significantly improve the efficiency and rate of the catalytic reaction. This technology is particularly suitable for treating furnace exhaust gases with high-temperature characteristics, utilizing both solar energy and waste heat from the exhaust gas as the driving energy for the reaction, thereby significantly reducing process energy consumption.

[0004] Therefore, developing a highly targeted, active, and stable nickel-supported semiconductor oxide-based photothermal catalyst and elucidating its application process in the efficient methanation conversion of carbon dioxide in flue gas is of urgent need and significant value for promoting the practical industrial application of carbon dioxide resource utilization technology. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing a highly efficient catalyst in the fields of thermal and photothermal catalysis, which is used to synthesize methane from carbon dioxide in flue gas through thermal and photothermal catalysis, so as to achieve a synthesis process with mild reaction conditions, environmental friendliness and low cost, and provide a new way for the high-value utilization of carbon dioxide in flue gas.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: Research has found that nickel metal is an excellent active center for carbon dioxide hydrogenation and can generate thermal energy through localized plasmon resonance, demonstrating great potential in the carbon dioxide methanation reaction. Semiconductor oxide supports such as titanium dioxide can excite reactants to form activating groups under light-driven conditions, reducing the activation energy of the reaction. Furthermore, they can stably disperse nickel nanoparticles, and their optical and electrical properties, in synergy with nickel, can further improve reaction efficiency. Therefore, this invention uses a specific method to prepare a highly efficient catalyst from Ni nanoparticles and semiconductor oxides such as titanium dioxide, and experimentally verified its key role in the photothermal catalytic carbon dioxide methanation in flue gas. This catalyst, in particular, overcomes the limitation of oxygen in flue gas on the reactivity of carbon dioxide methanation, effectively improving reaction efficiency and realizing the resource utilization of carbon dioxide.

[0007] A method for preparing a nickel-supported semiconductor oxide-based catalyst for the photothermal catalytic methanation of carbon dioxide in flue gas, wherein oxygen is present in the flue gas, the method comprising: S1. Disperse semiconductor oxide powder in deionized water and ultrasonically disperse to form a uniform suspension; S2. Add nickel salt solution to the obtained suspension and stir while soaking; S3. Dry the resulting solution until it is completely dehydrated to obtain the precursor powder; S4. Place the precursor powder in a muffle furnace and calcine it in air to obtain a calcined sample. S5. The calcined sample is placed in a tube furnace and reduced under a mixed gas of 10% H2 / Ar by volume to obtain the nickel-supported semiconductor oxide-based catalyst for carbon dioxide methanation in the photothermal catalytic flue gas.

[0008] In the above technical solution, the semiconductor oxide is one or more of cerium dioxide, titanium dioxide, and zirconium dioxide.

[0009] Furthermore, the nickel salt is preferably nickel nitrate.

[0010] Furthermore, the nickel loading in the catalyst ranges from 5 to 30 wt%, preferably 20 wt%, at which the catalyst exhibits the most prominent activity.

[0011] Furthermore, the calcination temperature range is 350-500 ℃, and the time is 1-5 h; preferably, calcination is carried out at 450 ℃ for 3 h.

[0012] Furthermore, the reduction temperature range is 300-600 ℃, and the time is 1~3h; preferably, the reduction treatment is carried out at 450 ℃ for 2h.

[0013] The catalyst described above is used in the application of carbon dioxide methanation in flue gas based on thermocatalysis or photothermal catalysis, wherein the flue gas contains oxygen.

[0014] The beneficial effects of this invention are: 1. The nickel-supported semiconductor oxide-based catalyst prepared in this invention, under optimal ratios and material selection (Ni loading of 20 wt%, semiconductor oxide selected as TiO2), in a photothermal catalytic system (without an external heat source), achieves a flux of 2.4 W / cm². 2 Under the specified light intensity, the carbon dioxide conversion rate in the simulated flue gas reached 70%, and the methane selectivity was >99%. Compared with the oxygen-free environment (16 vol% CO2, nitrogen as the balance gas) and the pure thermal catalytic synthesis of methane from simulated flue gas carbon dioxide at the same temperature and light intensity, the reaction activity was significantly improved, providing a more efficient catalytic method for the resource utilization of carbon dioxide in flue gas.

[0015] 2. This invention employs an impregnation, calcination, and reduction method to prepare a photothermal catalyst. While loading Ni nanoparticles, oxygen vacancies are generated simultaneously, and the synergistic effect of these two processes significantly promotes the photocatalytic reaction. This preparation method is simple and easy to implement, and the entire process does not involve any toxic substances, fully complying with the principles of green chemistry. It reduces production costs and potential environmental hazards, demonstrating significant environmental friendliness and sustainability.

[0016] 3. The photothermal catalytic carbon dioxide methanation reaction system of this invention features mild reaction conditions, simple operation, no need for an external heat source, and can be met under normal pressure. Furthermore, the byproducts of this reaction are only water and trace amounts of carbon monoxide. Its excellent activity and stability verify the advantages of this catalyst in treating carbon dioxide in flue gas, effectively meeting the resource utilization needs of carbon dioxide in flue gas. It is a green and efficient photothermal catalytic reaction system with broad application prospects. Attached Figure Description

[0017] Figure 1 HRTEM image and corresponding EDS image of the nickel-supported semiconductor oxide-based photothermal catalyst prepared in Example 1 of the present invention; Figure 2 The XRD patterns are of the nickel-supported semiconductor oxide-based photothermal catalysts prepared in Examples 1 and 2 of this invention. Figure 3 The ultraviolet absorption spectra of the nickel-supported semiconductor oxide-based photothermal catalysts prepared in Examples 1 and 2 of this invention are shown below. Figure 4 These are activity evaluation diagrams for reactions in Examples 4, 5, and 7 of this invention; Figure 5 These are activity evaluation diagrams for reactions in Examples 4 and 6 of the present invention; Figure 6 This is a stability evaluation diagram of the reaction in Example 4 of the present invention. Detailed Implementation

[0018] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of the present disclosure.

[0019] The simulated flue gas used in the following examples consisted of 16 vol% CO2, 4 vol% O2, with nitrogen as the balance gas; the catalytic performance of all samples was tested using the following methods: Pure thermocatalytic performance evaluation: 50 mg of catalyst was placed in a fixed quartz tube reactor with an inner diameter of 8 mm. The reactor was then purged with argon for 20 min to remove residual gas. A mixture of simulated flue gas and hydrogen was then introduced into the reactor, and the reactor was purged for 30 min to saturate the catalyst. The mixed gas was continuously introduced, and the total gas flow rate was controlled at 15 ml / min. -1 The heating power of the external heat source was adjusted, and the activity and product selectivity of the carbon dioxide methanation reaction in flue gas were tested at different temperatures. The gaseous products were analyzed using a GC-2014 C gas chromatograph.

[0020] Photothermal catalytic performance evaluation: 50 mg of catalyst was spread evenly in a flow reactor, forming a circular layer with a diameter of 18 mm. The reactor was then purged with argon for 20 min to remove residual gas. A mixture of simulated flue gas and hydrogen was then introduced into the reactor, and purging was continued for 30 min to saturate the catalyst. The total gas flow rate was maintained at 15 ml / min. -1 Irradiation with a xenon lamp in the absence of an external heat source was conducted. By adjusting the light intensity, the activity and product selectivity of the carbon dioxide methanation reaction in flue gas were tested under different light intensities. The gaseous products were analyzed using a GC-2014 C gas chromatograph.

[0021] Example 1: The 20Ni-80TiO2 photothermal catalyst was prepared by impregnation, calcination, and reduction. The specific steps are as follows: S1. Disperse 500 mg TiO2 powder in 30 mL of deionized water and ultrasonically disperse to form a uniform suspension.

[0022] S2. Add 12.5 mL of metallic nickel with a content of 10 mg / mL to the above solution. -1 The Ni(NO3)2 solution was immersed and stirred at 80 °C for 1 h.

[0023] S3. Place the obtained solution in an 80 ℃ oven and dry until completely dehydrated to obtain precursor powder.

[0024] S4. Place the precursor powder in a muffle furnace and calcine at 450 °C for 3 hours to obtain the calcined sample.

[0025] S5. The calcined sample was placed in a tube furnace and reduced at 450 °C for 2 h under a 10% H2 / Ar mixed gas to obtain the 20Ni-80TiO2 photothermal catalyst.

[0026] Example 2: The 20Ni-80CeO2 photocatalyst was prepared by impregnation, calcination, and reduction. The specific steps are as follows: S1. Disperse 500 mg CeO2 in 30 mL of deionized water and ultrasonically disperse to form a uniform suspension.

[0027] S2. Add 12.5 mL of metallic nickel with a content of 10 mg / mL to the above solution. -1 The Ni(NO3)2 solution was immersed and stirred at 80 °C for 1 h.

[0028] S3. Place the obtained solution in an 80 ℃ oven and dry until completely dehydrated to obtain precursor powder.

[0029] S4. Place the precursor powder in a muffle furnace and calcine at 450 °C for 3 hours to obtain the calcined sample.

[0030] S5. The calcined sample was placed in a tube furnace and reduced at 450 °C for 2 h under a 10% H2 / Ar mixed gas to obtain the 20Ni-80CeO2 photothermal catalyst.

[0031] Example 3: The 20Ni-80TiO2 photocatalyst was prepared by hydrothermal synthesis, and the specific steps are as follows: S1. 6 mL of metallic nickel with a content of 10 mg / mL -1 Ni(NO3)2 solution, 3 mL of 1 mol·L -1 TiCl4 solution, 0.5 mL concentrated hydrochloric acid, and 0.2 mol urea were dissolved in 100 mL deionized water.

[0032] S2. After stirring the above solution for 3 hours, transfer it to a hydrothermal reactor.

[0033] S3. Place the hydrothermal reactor in a 95℃ oven and keep it warm for 24 hours. After separating the solution, the precursor powder is obtained.

[0034] S4. Place the precursor powder in a muffle furnace and calcine at 450 °C for 3 hours to obtain the calcined sample.

[0035] S5. The calcined sample was placed in a tube furnace and reduced at 450 °C for 2 h under a 10% H2 / Ar mixed gas to obtain the 20Ni-80TiO2 photothermal catalyst.

[0036] The HRTEM image and corresponding EDS image of the nickel-supported semiconductor oxide-based photothermal catalyst prepared in Example 1 are shown below. Figure 1 As shown, the XRD patterns and UV absorption spectra of the catalysts prepared in Examples 1 and 2 are as follows. Figure 2 , Figure 3 As shown, it can be seen that the method of the present invention can obtain nickel-loaded semiconductor oxides, with nickel metal nanoparticles distributed on the surface of the semiconductor oxide nanoparticles.

[0037] Example 4: The 20Ni-80TiO2 prepared in Example 1 was used for photothermal synergistic catalysis to simulate the methanation reaction of carbon dioxide in flue gas. The specific steps are as follows: S1. Spread 50 mg of catalyst evenly in a flow reactor, forming a circular catalyst layer with a diameter of 18 mm.

[0038] S2. Purge the reactor with argon gas for 20 minutes to remove residual gas from the reactor.

[0039] S3. Introduce a mixture of simulated flue gas and hydrogen into the reactor (V). CO2 :V H2 (ratio = 1:4), purge for 30 min to saturate the catalyst adsorption, and continuously introduce the mixed gas while controlling the total gas flow rate at 15 ml·min. -1 .

[0040] S4. Irradiate with a xenon lamp in the absence of an external heat source. By adjusting the light intensity, test the activity and product selectivity of carbon dioxide methanation reaction under different light intensities. Analyze the gaseous products using a GC-2014 C gas chromatograph.

[0041] Example 5: The 20Ni-80TiO2 prepared in Example 1 was used for photothermal synergistic catalytic carbon dioxide methanation reaction. The specific steps are as follows: S1. Spread 50 mg of catalyst evenly in a flow reactor, forming a circular catalyst layer with a diameter of 18 mm.

[0042] S2. Purge the reactor with argon gas for 20 minutes to remove residual gas from the reactor.

[0043] S3. A mixture of carbon dioxide, hydrogen, and nitrogen in a certain proportion is introduced into the reactor (V CO2 :V H2(ratio = 1:4), purge for 30 min to saturate the catalyst adsorption, and continuously introduce the mixed gas while controlling the total gas flow rate at 15 ml·min. -1 .

[0044] S4. Irradiate with a xenon lamp in the absence of an external heat source. By adjusting the light intensity, test the activity and product selectivity of carbon dioxide methanation reaction under different light intensities. Analyze the gaseous products using a GC-2014 C gas chromatograph.

[0045] Example 6: The 20Ni-80TiO2 prepared in Example 1 was used for a pure thermocatalytic simulated carbon dioxide methanation reaction in flue gas. The specific steps are as follows: S1. Place 50 mg of catalyst in a fixed quartz tube reactor with an inner diameter of 8 mm.

[0046] S2. Purge the reactor with argon gas for 20 minutes to remove residual gas from the reactor.

[0047] S3. Introduce a mixture of simulated flue gas and hydrogen into the reactor (V). CO2 :V H2 (ratio = 1:4), purge for 30 min to saturate the catalyst adsorption, and continuously introduce the mixed gas while controlling the total gas flow rate at 15 ml·min. -1 .

[0048] S4. Adjust the heating power of the external heat source. By adjusting the power of the external heat source, test the activity and product selectivity of carbon dioxide methanation reaction at different temperatures. Analyze the gaseous products using a GC-2014 C gas chromatograph.

[0049] Example 7: The 20Ni-80TiO2 prepared in Example 3 was used for photothermal synergistic catalysis to simulate the methanation reaction of carbon dioxide in flue gas. The specific steps are as follows: S1. Spread 50 mg of catalyst evenly in a flow reactor, forming a circular catalyst layer with a diameter of 18 mm.

[0050] S2. Purge the reactor with argon gas for 20 minutes to remove residual gas from the reactor.

[0051] S3. Introduce a mixture of simulated flue gas and hydrogen into the reactor (V). CO2 :V H2 (ratio = 1:4), purge for 30 min to saturate the catalyst adsorption, and continuously introduce the mixed gas while controlling the total gas flow rate at 15 ml·min. -1 .

[0052] S4. Irradiate with a xenon lamp in the absence of an external heat source. By adjusting the light intensity, test the activity and product selectivity of carbon dioxide methanation reaction under different light intensities. Analyze the gaseous products using a GC-2014 C gas chromatograph.

[0053] The activity evaluation graphs for the reactions in Examples 4-7 are shown below. Figure 4 , Figure 5 As shown, the 20Ni-80TiO2 catalyst prepared by this invention exhibits both thermal and photothermal catalytic properties, and in particular, it can overcome the limitation of oxygen on the methanation activity of carbon dioxide, achieving a methanation activity of only 2.4 W / cm² without an external heat source. 2 Under the specified light intensity, the photothermal catalyst can catalyze a carbon dioxide conversion rate of 70% in simulated flue gas, with a methane selectivity >99%, significantly superior to that under anaerobic conditions or based on thermal catalysis. Furthermore, the byproducts in this reaction are only water and trace amounts of carbon monoxide, making this method green and efficient. The results also show that different preparation methods significantly affect the performance of the obtained product; the photothermal catalyst obtained using the method of this invention exhibits relatively superior catalytic performance.

[0054] In the catalyst obtained by this invention, Ni metal nanoparticles serve as hydrogenation sites for carbon dioxide. Under light-driven conditions, the semiconductor oxide material excites oxygen in the flue gas to combine with reactants, generating more reactive intermediates. The surface oxygen vacancies formed by the reduction treatment of the material further enhance the catalyst's adsorption and activation capabilities for reactants. Compared with traditional industrial synthesis, the photothermal catalysis technology of this invention has advantages such as mild reaction conditions, simple operation, and environmental friendliness. It provides an efficient and feasible route for the resource utilization of carbon dioxide and has broad application prospects.

[0055] The embodiments described above are merely some preferred embodiments of the present invention, and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A method for preparing a nickel-supported semiconductor oxide-based catalyst for the photothermal catalytic methanation of carbon dioxide in flue gas, characterized in that, The flue gas contains oxygen, and the method includes: S1. Disperse semiconductor oxide powder in deionized water and ultrasonically disperse to form a uniform suspension; S2. Add nickel salt solution to the obtained suspension and stir while soaking; S3. Dry the resulting solution until it is completely dehydrated to obtain the precursor powder; S4. Place the precursor powder in a muffle furnace and calcine it in air to obtain a calcined sample. S5. The calcined sample is placed in a tube furnace and reduced under a mixed gas of 10% H2 / Ar by volume to obtain the nickel-supported semiconductor oxide-based catalyst for carbon dioxide methanation in the photothermal catalytic flue gas.

2. The preparation method according to claim 1, characterized in that, The semiconductor oxide is one or more of cerium dioxide, titanium dioxide, and zirconium dioxide.

3. The preparation method according to claim 1, characterized in that, The nickel loading in the catalyst ranges from 5 to 30 wt%, preferably 20 wt%.

4. The preparation method according to claim 1, characterized in that, The calcination temperature range is 350-500 ℃, and the time is 1-5 h; preferably, calcination is carried out at 450 ℃ for 3 h.

5. The preparation method according to claim 1, characterized in that, The reduction temperature range is 300-600 ℃, and the time is 1~3h; preferably, the reduction treatment is performed at 450 ℃ for 2h.

6. A nickel-supported semiconductor oxide-based catalyst for the photothermal catalytic methanation of carbon dioxide in flue gas, characterized in that, Obtained by means of any one of claims 1-5.

7. The application of the catalyst as described in claim 6 in the photothermal catalytic carbon dioxide methanation in flue gas, characterized in that, The flue gas contains oxygen.

8. The application of the catalyst as described in claim 6 in the carbon dioxide methanation based on thermocatalytic flue gas, characterized in that, The flue gas contains oxygen.

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