High-performance photo-thermal coupling methane dry reforming catalyst as well as preparation method and application thereof

Abstract

The invention discloses a high-performance photo-thermal coupling methane dry reforming catalyst and a preparation method and application thereof.According to the catalyst, a nano organic zeolite structure serves as a precursor, the characteristics of porosity and high specific surface area of the zeolite structure are reserved after hydrogen reduction, metal dispersity is high, and reaction activity can be enhanced. The high-performance methane dry reforming reaction is realized under the condition of condensed light irradiation and heating (594 DEG C), the light-fuel efficiency is up to 32.4%, the hydrogen yield is up to 105.83 mmol min <-1 > g <-1 >, and the carbon monoxide yield is up to 128.17 mmol min <-1 > g <-1 >. In addition, due to the addition of cobalt, the alkalinity of the catalyst is improved, and activation of carbon dioxide is facilitated. The carbon shell limits the aggregation of the nano metal at high temperature, and due to the synergistic effect of Ni-Co, the carbon deposition amount of the reaction is obviously reduced, so that the catalyst has good durability.

Description

Technical Field

[0001] The present invention belongs to the technical field of solar fuel, and in particular relates to a high-performance photothermal coupled methane dry reforming catalyst and a preparation method and application thereof. Background Art

[0002] The large-scale burning of fossil fuels releases a large amount of carbon dioxide into the atmosphere, leading to global warming and a series of thorny environmental problems. In addition to studying how to reduce carbon dioxide emissions, the use of carbon dioxide to synthesize fuels takes into account both environmental protection and economy. Solar-driven carbon dioxide emission reduction is undoubtedly an attractive way to solve the current energy shortage and climate change problems at the same time because its heating source is green and environmentally friendly solar energy. Among various CO2 emission reduction technologies, the use of CH4 solar-driven CO2 emission reduction (i.e. methane dry reforming CH4+CO2=2CO+2H2, ΔH 298K =247kJ / mol) has unique advantages in mitigating global warming because the two main greenhouse gases CH4 and CO2 can be simultaneously converted into industrially valuable synthesis gas. For methane dry reforming catalysts, precious metals (Pt, Pd, Rh, Ru) have been widely studied and have been shown to perform well in methane dry reforming reactions, with high activity and excellent durability. However, the extremely high cost of precious metals makes it difficult to apply them on a large scale. Non-precious transition metals, especially nickel (Ni), also have the same high catalytic activity as precious metals. They are low-cost and abundant in reserves. However, nickel-based catalysts have serious sintering and coking problems and will quickly deactivate over time, which limits their large-scale application. On the other hand, how to utilize solar energy is also an urgent problem to be solved in the process of solar-driven carbon dioxide emission reduction. Summary of the invention

[0003] Purpose of the invention: The present invention aims to provide a method for preparing a high-performance photothermal coupled methane dry reforming catalyst, wherein cobalt is introduced into a pure nickel catalyst to form an alloy catalyst, and the synergistic effect of nickel and cobalt reduces carbon deposition during the reaction; the carbon shell obtained by carbonizing the organic zeolite structure limits the migration of catalyst particles at high temperatures, thereby reducing the effect of catalyst sintering on the reaction activity; the present invention also aims to provide a high-performance photothermal coupled methane dry reforming catalyst, which shows high spectral absorption capacity in the ultraviolet-visible light range and realizes high-performance methane dry reforming reaction under conditions of concentrated irradiation and heating; the present invention also aims to provide the application of the high-performance photothermal coupled methane dry reforming catalyst in the photothermal catalytic CH4-CO2 reforming reaction.

[0004] Technical solution: The preparation method of the high-performance photothermal coupled methane dry reforming catalyst described in the present invention comprises: partially replacing the position of cobalt in ZIF-67 with nickel to obtain a nickel-cobalt nano-metal organic zeolite structure precursor, and then reducing the precursor under a reducing atmosphere to precipitate a nano-alloy to obtain a NiCo@C-Al2O3 catalyst.

[0005] Furthermore, the preparation process of the precursor includes:

[0006] Dissolving nickel nitrate hexahydrate and cobalt nitrate hexahydrate in a solvent, stirring to fully dissolve the metal source to form a first solution, and adding γ-Al2O3 to the first solution to form a suspension;

[0007] dissolving dimethylimidazole in a solvent and stirring to form a second solution;

[0008] The suspension and the second solution are mixed and stirred, and after centrifugation, the precipitate is washed and dried to obtain a nickel-cobalt nano-metal organic zeolite structure precursor.

[0009] Furthermore, the heating rate during the reduction process is 0.3-0.5°C / min. After heating to 700-800°C, the temperature is kept for 3-5 hours. The reducing atmosphere is a mixed atmosphere of H2 and N2, and the volume ratio of the two is 1:8-9.

[0010] Furthermore, the molar ratio of the cobalt nitrate hexahydrate to the nickel nitrate hexahydrate is 0.5-3, and the mass ratio of the 2-methylimidazole to γ-Al2O3 is 25-20:1.

[0011] Furthermore, the suspension and the second solution are mixed and stirred for 7-10 hours, and then allowed to stand for 1-3 hours after stirring. The stirring time required to form the first solution, the suspension or the second solution is 5-20 minutes.

[0012] The high-performance photothermal coupled methane dry reforming catalyst can be used in photothermal catalytic CH4-CO2 reforming reaction.

[0013] The steps of preparing solar fuel by photothermal catalytic CH4-CO2 reforming reaction include:

[0014] (1) A Ni-psnts@CeO2 composite catalyst was placed in a photothermal catalytic reactor, and a CH4 / CO2 / N2 mixed gas with a volume content of 40 / 40 / 20% was introduced under concentrated radiation.

[0015] (2) The gas at the reactor outlet is introduced into a gas chromatograph for gas type and content analysis, and quantification is performed based on the size of the peak area in the chromatographic detection diagram.

[0016] Principle of the invention: The catalyst of the present invention introduces cobalt on the basis of pure nickel catalyst to form an alloy catalyst. The synergistic effect of nickel and cobalt reduces carbon deposition during the reaction process; the carbon shell obtained by carbonizing the organic zeolite structure limits the migration of catalyst particles at high temperatures, reduces the effect of catalyst sintering on the reaction activity, and makes photothermal catalysis have a higher reaction rate than thermal catalysis at the same temperature, so it has a broader development prospect.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0018] (1)Ni X Co Y -CZIF / Al2O3 composite catalyst has high photothermal catalytic activity and strong stability; the composite photothermal catalyst exhibits high photothermal catalytic activity and stability under sunlight simulated by a xenon lamp, and the hydrogen yield reaches 105.83mmol min after 10h of continuous reaction. -1 g -1 The carbon monoxide yield reached 128.17 mmol min -1 g -1 , light-fuel efficiency up to 32.4%;

[0019] (2) The catalyst preparation method is simple and low-cost, and can be driven by solar energy as the only energy source, realizing the integration of greenhouse gas conversion, solar fuel preparation and solar energy storage. It avoids the high energy consumption and secondary emission of greenhouse gases in traditional thermal catalysis, and is beneficial to environmental protection and new energy development. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the spectral absorbance of catalysts with different NiCo ratios in the UV-visible band (400nm to 2500nm);

[0021] Figure 2 is the SEM image of the catalyst precursor Ni1Co2-ZIF / Al2O3;

[0022] Figure 3 It is the SEM image of Ni1Co2-CZIF / Al2O3;

[0023] Figure 4 It's Ni X Co Y -XRD pattern of CZIF / Al2O3;

[0024] Figure 5 It's Ni X Co Y -Photothermal catalytic reaction and production rate diagram of CZIF / Al2O3. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0026] Example 1

[0027] The preparation process of the catalyst is as follows:

[0028] (1) A total of 5.46 g of Ni(NO3)2·6H2O and Co(NO3)2·6H2O (molar ratio = 1:2) as metal sources were completely dissolved in 40 ml of methanol.

[0029] (2) Dissolve 4.8 g of 2-methylimidazole and 0.2 g of γ-Al2O3 in 30 ml of methanol.

[0030] (3) The two solutions of step (1) and (2) were mixed thoroughly, and then magnetically stirred at 300 rpm for 8 hours.

[0031] (4) After the stirring, the solution was allowed to stand at room temperature of 27°C for 2 hours, and then the precipitate was collected by centrifugation and washed three times with methanol and ethanol respectively.

[0032] (5) The precipitate after centrifugation was dried in a forced air drying oven at 80°C overnight to obtain a Ni1Co2-ZIF / Al2O3 precursor.

[0033] (6) Ni1Co2-ZIF / Al2O3 was placed in a tubular furnace and purged with a reducing atmosphere (10% H2, 90% N2) at a flow rate of 400 ml / min for one hour. Then, the mixture was heated to 750°C at a heating rate of 1°C / min for 4 hours to obtain a Ni1Co2@CZIF-Al2O3 catalyst.

[0034] Example 2

[0035] The preparation process of the catalyst is the same as that of Example 1, except that the molar ratio of Ni(NO3)2·6H2O to Co(NO3)2·6H2O is 1:1.

[0036] Example 3

[0037] The preparation process of the catalyst is the same as that of Example 1, except that the molar ratio of Ni(NO3)2·6H2O to Co(NO3)2·6H2O is 1:3.

[0038] Example 3

[0039] The preparation process of the catalyst is the same as that of Example 1, except that the molar ratio of Ni(NO3)2·6H2O to Co(NO3)2·6H2O is 2:1.

[0040] Comparative Example 1

[0041] The preparation process of the catalyst is the same as that of Example 1, except that the molar ratio of Ni(NO3)2·6H2O to Co(NO3)2·6H2O is 0:1.

[0042] Comparative Example 2

[0043] The preparation process of the catalyst is the same as that of Example 1, except that the molar ratio of Ni(NO3)2·6H2O to Co(NO3)2·6H2O is 1:0.

[0044] Photothermal catalytic activity test:

[0045] (1) A self-made photothermal catalytic reactor with an inner diameter of 6 mm was loaded with 17 mg of catalyst and heated at 100 ml min under 12 W concentrated light irradiation. -1 A CH4 / CO2 / N2 mixture with a volume content of 40 / 40 / 20% was introduced at a flow rate.

[0046] (2) The gas at the reactor outlet is introduced into a gas chromatograph for gas type and content analysis, and quantification is performed based on the size of the peak area in the chromatographic detection diagram.

[0047] Thermal catalytic activity test:

[0048] 17 mg of the catalyst was placed in a tube furnace and heated at 100 ml min -1 A CH4 / CO2 / N2 mixed gas with a volume content of 40 / 40 / 20% is introduced at a flow rate and then heated to the reaction temperature using electric heating (without light). The gas at the outlet of the tube furnace is introduced into a gas chromatograph for gas type and content analysis, and quantification is performed based on the size of the peak area in the chromatographic detection diagram.

[0049] From the spectral absorption results of catalysts with different NiCo ratios ( Figure 1 ) It can be seen that the overall absorption performance in the 400-2500nm band is good, which is the result of the NiCo plasmon effect on the catalyst surface enhancing the spectral absorption.

[0050] from Figure 2 It can be seen from the SEM image in that the precursor Ni1Co2-ZIF / Al2O3 prepared in Example 1 is in the shape of a block.

[0051] from Figure 3 It can be seen from the SEM image in that after the reduction of Ni1Co2-CZIF / Al2O3, Ni particles are formed on the catalyst surface.

[0052] from Figure 4 It can be seen from the XRD analysis results that Ni X Co YThe diffraction peaks of metallic Ni and support in -CZIF / Al2O3 are obvious, which indicates that Ni exists in the catalyst in the form of metallic phase.

[0053] from Figure 5 It can be seen that Ni1Co2-CZIF / Al2O3 exhibits the highest catalytic activity. High-performance methane dry reforming reaction was achieved under concentrated light irradiation heating conditions (594°C), with a light-to-fuel efficiency of up to 32.4% and a hydrogen yield of 105.83 mmol min -1 g -1 The carbon monoxide yield reached 128.17 mmol min -1 g -1 In addition, the addition of cobalt improves the basicity of the catalyst, which is more conducive to the activation of carbon dioxide. The carbon shell limits the aggregation of nanometals at high temperatures, and due to the synergistic effect of Ni-Co, the amount of carbon deposits in the reaction is significantly reduced, so the catalyst has good durability.

Claims

1. A method for preparing a high-performance photothermal coupled methane dry reforming catalyst, characterized in that: The method comprises: partially replacing the position of cobalt in ZIF-67 with nickel to prepare a nickel-cobalt nano-metal organic zeolite structure precursor, and then reducing the precursor in a reducing atmosphere to precipitate a nano alloy to prepare a NiCo@C-Al2O3 catalyst.

2. The method for preparing a high-performance photothermal coupled methane dry reforming catalyst according to claim 1, characterized in that: The preparation process of the precursor comprises: Dissolving nickel nitrate hexahydrate and cobalt nitrate hexahydrate in a solvent, stirring to fully dissolve the metal source to form a first solution, and adding γ-Al2O3 to the first solution to form a suspension; dissolving dimethylimidazole in a solvent and stirring to form a second solution; The suspension and the second solution are mixed and stirred, and after centrifugation, the precipitate is washed and dried to obtain a nickel-cobalt nano-metal organic zeolite structure precursor.

3. The method for preparing a high-performance photothermal coupled methane dry reforming catalyst according to claim 1, characterized in that: The heating rate during the reduction process is 0.3-0.5°C / min. After heating to 700-800°C, keep warm for 3-5h.

4. The method for preparing a high-performance photothermal coupled methane dry reforming catalyst according to claim 2, characterized in that: The molar ratio of the cobalt nitrate hexahydrate to the nickel nitrate hexahydrate is 0.5-3.

5. The method for preparing a high-performance photothermal coupled methane dry reforming catalyst according to claim 2, characterized in that: The mass ratio of 2-methylimidazole to γ-Al2O3 is 25-20:

1.

6. The method for preparing a high-performance photothermal coupled methane dry reforming catalyst according to claim 2, characterized in that: The suspension and the second solution are mixed and stirred for 7-10 hours, and then allowed to stand for 1-3 hours.

7. The method for preparing a high-performance photothermal coupled methane dry reforming catalyst according to claim 2, characterized in that: The stirring time required to form the first solution, suspension or second solution is 5-20 minutes.

8. The method for preparing a high-performance photothermal coupled methane dry reforming catalyst according to claim 2, characterized in that: The reducing atmosphere is a mixed atmosphere of H2 and N2, and the volume ratio of the two is 1:8-9.

9. A high-performance photothermal coupled methane dry reforming catalyst, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the high-performance photothermal coupled methane dry reforming catalyst according to claim 9 in a photothermal catalytic CH4-CO2 reforming reaction.

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