Metal-loaded titanium dioxide photo-thermal catalyst, preparation method thereof and photo-thermal catalytic carbon dioxide methanation application

Abstract

The invention relates to a metal-loaded titanium dioxide photo-thermal catalyst, a preparation method thereof and application thereof in photo-thermal catalysis of methanation of carbon dioxide. The metal-TiO2 photo-thermal catalyst is prepared by pre-reduction treatment of titanium dioxide, impregnation of loaded metal and combination of a one-step annealing method. The pre-reduction treatment can provide more oxygen vacancy defects for TiO2, and the one-step annealing treatment keeps oxygen vacancies formed by the pre-reduction treatment on the material, so that overgrowth of crystal grains caused by calcination and damage to the TiO2 oxygen vacancies are avoided, and the adsorption and activation capacities of the catalyst on reactants are enhanced. The preparation process is simple, the cost is low, and in the photo-thermal catalytic carbon dioxide methanation reaction, compared with a TiO2 loaded metal catalyst which is not pretreated, the TiO2 loaded metal catalyst shows more efficient carbon dioxide conversion capacity. Besides, compared with pure thermocatalysis, the method disclosed by the invention has the advantages of milder reaction conditions, lower energy consumption and environmental friendliness, 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 photothermal catalytic synthesis, specifically relating to a metal-supported titanium dioxide photothermal catalyst, its preparation method, and its application in photothermal catalytic carbon dioxide methanation. Background Technology

[0002] Carbon dioxide, as a major greenhouse gas, contributes to global warming due to excessive emissions, making carbon emission reduction a consensus in the international community. Catalytically converting carbon dioxide into high-value-added chemicals is a key pathway to achieving carbon recycling. Among these, carbon dioxide methanation (CO2 + 4H2 → CH4 + 2H2O) can convert CO2 into methane fuel, offering both emission reduction and energy regeneration benefits. Methane, as a clean energy carrier, is in high demand and easy to store and transport; therefore, carbon dioxide methanation is considered one of the most promising CO2 conversion technologies. However, due to the stable chemical properties of CO2, direct conversion faces kinetic barriers, requiring highly efficient catalysts to lower the reaction energy barrier.

[0003] Titanium dioxide (TiO2), as a low-cost and stable semiconductor metal oxide support, possesses a certain degree of photoresponsiveness, effectively utilizing light energy to generate electron-hole pairs, thereby participating in reduction reactions. Furthermore, it can strongly interact with active metals, inhibiting sintering. Regarding the selection of active components, while noble metals (such as Ru and Pd) exhibit high activity, their cost limits their large-scale application. Non-noble metals such as nickel, iron, and cobalt, on the other hand, are inexpensive and demonstrate high activity and selectivity for methanation reactions, making them ideal alternatives. However, traditional Ni-based catalysts exhibit insufficient activity at low temperatures and are prone to deactivation due to carbon deposition, necessitating performance improvements through support optimization and structural design.

[0004] Utilizing solar energy to drive carbon dioxide methanation can reduce dependence on fossil fuels. Photothermal synergistic catalysis technology can directly convert light energy into heat energy, achieving reaction-driven operation within a mild temperature range (200-400℃). Existing photothermal catalysis systems often face problems such as low photothermal conversion efficiency and weak catalyst response to infrared light.

[0005] Therefore, developing a novel photothermal catalyst supported on titanium dioxide and other metals, possessing high photothermal conversion efficiency, excellent infrared absorption capability, and low-temperature methanation activity, is of great significance for achieving efficient and stable utilization of solar energy and promoting the resource utilization of carbon dioxide. This invention addresses the above needs by designing a TiO2-supported metal catalyst with a simple preparation method and low cost, capable of achieving highly selective carbon dioxide methanation under direct sunlight. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a metal-supported titanium dioxide photothermal catalyst and its preparation method, and using it for photothermal catalytic carbon dioxide methanation to achieve a simple and low-cost synthesis process, providing a new approach for the high-value utilization of low-temperature carbon dioxide.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a metal-supported titanium dioxide photothermal catalyst, comprising: S1. Place TiO2 powder in a tube furnace and anneal it in a 10% (by volume) H2 / Ar mixture or in an argon atmosphere mixed with NaBH4 particles to obtain pre-reduction treatment, thus obtaining pretreated TiO2. x ; S3, pre-treated TiO x Dispersed in deionized water, ultrasonically dispersed to form a uniform suspension; S4. Add a metal salt solution to the suspension and stir while soaking. S5. Dry the resulting solution until it is completely dehydrated to obtain the precursor powder; S6. The precursor powder is placed in a tube furnace and reduced under a H2 / Ar mixed gas with a volume percentage of 10% to obtain the nickel-loaded titanium dioxide photothermal catalyst.

[0008] In the above technical solution, the mass ratio of TiO2 to NaBH4 in S1 is 3:1 to 10:1.

[0009] Furthermore, in S1, TiO2 and NaBH4 particles are mixed in argon gas and annealed at a temperature of 300-450 °C for 1-5 h; preferably, the treatment is carried out at 400 °C for 3 h.

[0010] Furthermore, the TiO2 in S1 is annealed in a 10% (by volume) H2 / Ar mixed gas at a temperature of 500-700°C for 1-5 hours; preferably at 600°C for 3 hours.

[0011] Furthermore, the metal salt is one or more nitrates, chlorides, or carbonates selected from nickel, iron, cobalt, platinum, palladium, and ruthenium, preferably nickel nitrate. The metal loading in the photothermal catalyst is 5-20 wt%, preferably 15 wt%.

[0012] Furthermore, the reduction temperature range of the precursor powder in S6 is 300-500 ℃, and the time is 1~3h; preferably, it is reduced at 400 ℃ for 2h.

[0013] In the above scheme, metals (such as Ni) are excellent active centers for carbon dioxide hydrogenation and can generate heat energy through localized plasmon resonance, promoting the forward reaction. TiO2, as a cheap and stable semiconductor material, has a certain photoresponsiveness. By constructing oxygen vacancies through pre-reduction treatment, the photoresponsive range of TiO2 can be effectively broadened, thereby improving the utilization rate of solar energy. It can also serve as an active site to promote the adsorption and activation of CO2 molecules. The supported catalyst prepared by combining these two methods forms a strong metal-oxide substrate interaction, which can effectively promote the reaction. The one-step annealing method burns away nitrate while reducing the metal, retaining the oxygen vacancy defects formed by the pre-reduction treatment, avoiding the destruction of oxygen vacancies on the support by calcination, and inhibiting the excessive growth of metal grains. Therefore, this invention uses pre-reduced TiO2 to support metal and prepares a highly efficient photothermal catalyst through a one-step annealing method, and verifies its key role in photothermal catalytic carbon dioxide methanation through experiments. This catalyst can effectively improve the reaction efficiency and realize the resource utilization of carbon dioxide.

[0014] The beneficial effects of this invention include at least the following: 1. This invention employs a pre-reduction method to treat TiO2, generating a large number of oxygen vacancies. Following metal loading and subsequent annealing, the oxygen vacancies are retained while excessive metal particle growth is suppressed. This preparation method is simple and easy to operate, has prospects for large-scale production, and reduces production costs and material waste. Taking nickel as an example, in the photothermal catalytic carbon dioxide methanation reaction, at 3.2 W / cm²... 2 Under light intensity, the methane yield is greater than 100 mmol·g cal -1 ·h -1 This improves the activity of carbon dioxide methanation reaction, has significant sustainability, and provides a more efficient catalytic means for the resource utilization of carbon dioxide.

[0015] 2. 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 meet requirements under normal pressure. Its excellent catalytic activity and stability verify the advantages of this catalyst for carbon dioxide methanation, making it a green and efficient photothermal catalytic reaction system with broad application prospects. Attached Figure Description

[0016] Figure 1 TiO2 prepared in Example 1 of this invention x HRTEM image; Figure 2 TiO2 prepared in Example 1 of this invention x ESR diagram of TiO2 without pre-reduction treatment; Figure 3Ni-TiO prepared in Example 1 of this invention x XPS plot of photothermal catalyst; Figure 4 Ni-TiO prepared in Example 1 of this invention x Photothermal catalyst, TiO2 obtained by pre-reduction x And XRD patterns of TiO2 without pre-reduction treatment; Figure 5 Ni-TiO prepared in Example 1 of this invention x Photothermal catalyst, TiO2 obtained by pre-reduction x Raman spectrum of TiO2 without pre-reduction treatment; Figure 6 This is a stability evaluation graph for the performance test of Embodiment 1 of the present invention. Detailed Implementation

[0017] 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.

[0018] Example 1: Preparation of 15Ni-85TiO by high-temperature hydrogen pre-reduction of TiO2 for Ni loading followed by one-step annealing. x Photothermal catalyst, the specific steps are as follows: S1. TiO2 powder was placed in a tube furnace and reduced at 600 °C under a 10% H2 / Ar mixed gas for 3 h to obtain TiO2. x .

[0019] S2, Add 500 mg TiO x Disperse in 30 ml of deionized water and ultrasonically disperse to form a uniform suspension.

[0020] S3. Add a certain proportion of nickel nitrate (Ni(NO3)2) solution to the above solution, so that Ni metal accounts for 15wt% of the total catalyst, and impregnate and stir at 80 °C for 1h.

[0021] S4. Place the obtained solution in an 80 ℃ oven and dry until completely dehydrated to obtain precursor powder.

[0022] S5. The precursor powder is placed in a tube furnace and reduced at 400°C under a 10% H2 / Ar mixed gas for 2 h to obtain the photothermal catalyst.

[0023] Ni-TiO2 prepared x Photothermal catalyst, TiO2 obtained by pre-reduction x And partial characterization data of TiO2 without pre-reduction treatment, such as Figures 1-5As shown in the figure, it can be seen that the TiO2 obtained by pre-reduction... x The surface has an amorphous layer with oxygen vacancies and Ti. 3+ The signal is obvious, and the Raman characteristic peaks are significantly lower than those of TiO2 without pre-reduction. The pre-reduced TiO2 shows a clear decrease in these peaks. x After being impregnated and mixed with Ni(NO3)2 and reduced at 400℃, the XRD pattern showed that Ni was in a metallic state, while the XPS pattern showed that the catalyst surface had a mixed state of metal and oxide, which may be because the metallic nickel is small and the material surface is oxidized.

[0024] Example 2: Preparation of 15Ni-85TiO by pre-reduction of TiO2 with NaBH4 followed by one-step annealing. x Photothermal catalyst, the specific steps are as follows: S1. TiO2 powder and NaBH4 particles were placed in a tube furnace at a mass ratio of 5:1 and reduced at 400 °C under argon for 3 h to obtain TiO2. x .

[0025] S2, Add 500 mg TiO x Disperse in 30 ml of deionized water and ultrasonically disperse to form a uniform suspension.

[0026] S3. Add a certain proportion of nickel nitrate (Ni(NO3)2) solution to the above solution, so that Ni metal accounts for 15wt% of the total catalyst, and impregnate and stir at 80 °C for 1h.

[0027] S4. Place the obtained solution in an 80 ℃ oven and dry until completely dehydrated to obtain precursor powder.

[0028] S5. The precursor powder is placed in a tube furnace and reduced at 400°C under a 10% H2 / Ar mixed gas for 2 h to obtain the photothermal catalyst.

[0029] Comparative Example 1: A 15Ni-85TiO2 photothermal catalyst was prepared by loading Ni onto TiO2 without pre-reduction treatment and then annealing it. This catalyst was then used for photothermal catalytic carbon dioxide methanation. The specific steps are as follows: S1. Disperse 500mg TiO2 in 30 ml of deionized water and ultrasonically disperse to form a uniform suspension.

[0030] S2. Add a certain proportion of nickel nitrate (Ni(NO3)2) solution to the above solution, so that Ni metal accounts for 15wt% of the total catalyst, and impregnate and stir at 80 °C for 1h.

[0031] S3. Place the obtained solution in an 80 ℃ oven and dry until completely dehydrated to obtain precursor powder.

[0032] S4. The precursor powder is placed in a tube furnace and reduced at 400°C under a 10% H2 / Ar mixed gas for 2 h to obtain the photothermal catalyst.

[0033] Comparative Example 2: A 15Ni-85TiOx photothermal catalyst was prepared by high-temperature pre-reduction of TiO2 with hydrogen followed by calcination reduction, and then used for photothermal catalytic carbon dioxide methanation. The specific steps are as follows: S1. TiO2 powder and NaBH4 particles were placed in a tube furnace at a mass ratio of 5:1 and reduced at 400 °C under argon for 3 h to obtain TiO2. x .

[0034] S2, Add 500 mg TiO x Disperse in 30 ml of deionized water and ultrasonically disperse to form a uniform suspension.

[0035] S3. Add a certain proportion of nickel nitrate (Ni(NO3)2) solution to the above solution, so that Ni metal accounts for 15wt% of the total catalyst, and impregnate and stir at 80 °C for 1h.

[0036] S4. Place the obtained solution in an 80 ℃ oven and dry until completely dehydrated to obtain precursor powder.

[0037] S5. Place the precursor powder in a muffle furnace and calcine it in air at 400°C for 3 h to obtain the calcined sample.

[0038] S6. Place the calcined sample in a tube furnace and reduce it at 400℃ under a 10% H2 / Ar mixed gas for 2 h to obtain the photothermal catalyst.

[0039] Performance testing: 25 mg of catalyst was spread evenly in a flow reactor, forming a circular layer with a diameter of 15 mm. The reactor was then purged with argon for 20 min to remove residual gas. A mixture of carbon dioxide (20 vol%) and hydrogen (80 vol%) 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 20 ml / min. -1 The reaction was conducted under xenon lamp irradiation without an external heat source. 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. In the stability test, samples were taken every 0.5 hours for 24 hours. The experimental results are shown in Table 1 and... Figure 6The results showed that the catalyst prepared by the one-step annealing method after pre-reduction treatment of titanium dioxide with nickel loading exhibited significantly improved activity under the same test conditions, and different pre-reduction treatment methods led to differences in selectivity. The scheme of pre-reducing TiO2 first, then loading Ni, followed by one-step annealing, as described in this invention, is more conducive to obtaining a highly efficient photothermal catalyst, which can effectively improve the reaction activity of carbon dioxide methanation, especially when using high-temperature hydrogen pre-reduction treatment, the effect is even better. Furthermore, the one-step annealing method of this invention after Ni loading, compared to the calcination in air as described in prior art 2, better protects some of the oxygen vacancies generated by the pre-reduced titanium dioxide, which is beneficial to performance improvement.

[0040] Table 1. Examples 1 and 2 and Comparative Examples 1 and 2 at 3.2 W / cm² 2 Product yield and selectivity under light intensity.

[0041]

Claims

1. A method for preparing a metal-supported titanium dioxide photothermal catalyst, characterized in that, include: S1. Place TiO2 powder in a tube furnace and anneal it in a 10% (by volume) H2 / Ar mixture or in an argon atmosphere mixed with NaBH4 particles to obtain pre-reduction treatment, thus obtaining pretreated TiO2. x ; S3, pre-treated TiO x Dispersed in deionized water, ultrasonically dispersed to form a uniform suspension; S4. Add a metal salt solution to the suspension and stir while soaking. S5. Dry the resulting solution until it is completely dehydrated to obtain the precursor powder; S6. The precursor powder is placed in a tube furnace and reduced under a H2 / Ar mixed gas with a volume percentage of 10% to obtain the titanium dioxide photothermal catalyst with the supported metal.

2. The preparation method according to claim 1, characterized in that, The mass ratio of TiO2 to NaBH4 is 3:1 to 10:

1.

3. The preparation method according to claim 1, characterized in that, In S1, TiO2 and NaBH4 particles are mixed in argon gas and annealed at 300-450 ℃ for 1-5 h; preferably, the treatment is carried out at 400 ℃ for 3 h.

4. The preparation method according to claim 1, characterized in that, In S1, TiO2 is annealed in a 10% (by volume) H2 / Ar mixture at a temperature of 500-700 °C for 1-5 h; preferably at 600 °C for 3 h.

5. The preparation method according to claim 1, characterized in that, The metal salt mentioned in S4 is one or more nitrates, chlorides or carbonates of nickel, iron, cobalt, platinum, palladium or ruthenium, preferably nickel nitrate.

6. The preparation method according to claim 1, characterized in that, The metal loading in the photothermal catalyst is 5-20 wt%, preferably 15 wt%.

7. The preparation method according to claim 1, characterized in that, The precursor powder reduction temperature range in S6 is 300-500 ℃, and the time is 1~3h; preferably, it is reduced at 400 ℃ for 2h.

8. A metal-supported titanium dioxide photothermal catalyst, characterized in that, It is prepared by the method described in any one of claims 1-7.

9. The application of the photothermal catalyst as described in claim 6 in photothermal catalytic carbon dioxide methanation.

Images