Preparation method of iron-based catalyst fe / cuo2 and application thereof in co2 catalytic hydrogenation reaction
By preparing Fe/CeO2 catalysts through a deposition-precipitation method with controlled iron loading on a nano-octahedral support, the problem of insufficient activity and stability of iron-based catalysts in the reverse water-gas shift reaction was solved, achieving efficient CO generation and long-term stable operation.
Patent Information
- Application Number
- CN202411842465.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-13
- Publication Date
- 2026-02-27
- Estimated Expiration
- 2044-12-13
AI Technical Summary
Existing iron-based catalysts suffer from low catalytic activity and poor stability in reverse water-gas shift reactions. In particular, they are prone to agglomeration and phase transition at high temperatures and high H2/CO2 ratios, which affects the characteristics of active sites.
Highly dispersed iron-based catalyst Fe/CeO2 was prepared by deposition-precipitation method. By controlling the iron loading on the nano-octahedral support and preparing Ce(OH)x support by hydrothermal method, strong interactions were formed, achieving high dispersion of iron and local structural control.
The CO generation rate reached 28.99 mmol CO·gFe⁻¹·s⁻¹ at 600℃, and it exhibited excellent stability in the 150h stability test. The catalytic activity and selectivity were significantly improved, and the cost was low.
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Figure CN119565621B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of material science, and particularly relates to a preparation method of a high-dispersion, stable and efficient Fe / CeO2 iron-based catalyst and application of the Fe / CeO2 iron-based catalyst in a CO2 catalytic hydrogenation reaction. BACKGROUND
[0002] In recent years, with the increasing seriousness of the greenhouse effect caused by a large amount of carbon dioxide emissions, the adverse effects caused by a large amount of emissions are one of the biggest challenges faced by mankind in recent years. An effective method to solve this problem is to chemically convert carbon dioxide into value-added products. In this case, the reverse water gas shift (RWGS) reaction shows many advantages. For example, the reverse water gas shift reaction can realize the conversion and utilization of carbon dioxide, which helps to alleviate the greenhouse effect and reduce carbon emissions. At the same time, carbon monoxide as a product can be reused as a reactant for the production of methanol and hydrocarbons, improving the efficiency of resource utilization. Compared with traditional fossil fuel combustion, the waste gas produced by the reverse water gas shift reaction has a lower carbon dioxide content, and has less impact on the environment. In addition, by optimizing the reaction conditions and the use of catalysts, waste gas emissions and energy consumption can be further reduced. The reverse water gas shift reaction has high flexibility and can be adjusted and optimized according to different needs and reaction conditions. For example, by changing the type of catalyst and reaction conditions, the selectivity and conversion rate of the product can be controlled. In summary, the reverse water gas shift reaction has made significant progress in the fields of catalyst research, reaction condition optimization and application expansion. Its advantages include high resource utilization efficiency, environmental friendliness and high flexibility. In the future, with the development of new energy and green chemistry and the continuous progress of technology, the reverse water gas reaction will be applied and promoted in more fields.
[0003] In the past decades, researchers have been devoted to the facile preparation of high-performance catalysts for reverse water-gas shift reaction (RWGS). Supported noble metal catalysts are favored for their advantages in H2 activation and stability during the reaction. However, non-noble metal catalysts show greater potential for industrial applications, although they have their own advantages and disadvantages. Copper catalysts exhibit excellent activity at low temperatures, but often face the problems of deactivation and structural evolution. The lower CO selectivity of nickel-based catalysts is a challenge, while the catalytic activity of molybdenum-based catalysts needs to be further improved. Iron-based catalysts are known for their high performance at high temperatures and complex structures, and the overall performance of RWGS catalysts can be effectively improved by adjusting the geometric properties (such as metal dispersion: 15Cu / CeO2; metal-support interface: 0.5Ir / MoO3, KPt / SiO2) and electronic structure (such as Pt1Fe1 / CeO2, PtNi / ZrO2). Although some progress has been made in the synthesis method, it is still very urgent to develop new non-precious metal catalysts with high catalytic activity, selectivity and thermal stability.
[0004] Iron-based catalysts are concerned for their thermal stability and low cost in RWGS reaction, but their catalytic activity is still inferior to the most advanced catalysts. Although researchers have achieved different degrees of improvement by adjusting the size, morphology and phase of iron catalysts, at high temperature and high H2 / CO2 ratio, iron-based catalysts are prone to agglomeration, phase transition and carbon deposition, which makes the characteristics of active sites still controversial. SUMMARY
[0005] In view of the above deficiencies of the prior art and the complexity of the structure of iron-based catalysts, the present application provides a preparation method of a highly dispersed, stable and efficient iron-based catalyst Fe / CeO2 and its application in CO2 catalytic hydrogenation reaction. The present application controls the dispersion and local structure of iron loading on nano-octahedral carriers, and the CO generation rate of 1Fe / CeO2 catalyst at 600℃ can reach 28.99 mmol CO ·g Fe -1 ·s -1 at the same time, it shows excellent stability during the stability test of 150h.
[0006] The preparation method of the iron-based catalyst Fe / CeO2 of the present application adopts deposition-precipitation method, which comprises the following steps:
[0007] Ce(OH) xThe support was dispersed in deionized water under vigorous stirring, then 0.01 mol / L aqueous solution of iron nitrate nonahydrate was added dropwise, the iron loading was adjusted by the mass of iron nitrate nonahydrate added, and the pH value of the system was adjusted to 9.0 by adding sodium carbonate solution, stirred at room temperature for 2 h, and then aged at room temperature for 2 h; the precipitate was filtered, washed with deionized water, and continuously dried at 60 °C for 12 h, and the dried sample was further calcined to obtain the iron-based catalyst Fe / CeO2.
[0008] The Ce(OH) x The morphology of the support includes one or more of the following: Ce(OH) x nanooctahedron support, Ce(OH) x nanorod support, Ce(OH) x one or more of the following: Ce(OH) x nanooctahedron support.
[0009] Further, the Ce(OH) x The nanooctahedron support is prepared by a method comprising the following steps:
[0010] 1 mol / L sodium hydroxide solution was added to 5 mol / L cerium nitrate hexahydrate solution (mass of sodium hydroxide: mass of cerium nitrate hexahydrate = 1.4:1), and stirred vigorously for 30 minutes to form a white slurry solution; the mixture was transferred to a Teflon-lined autoclave, and then subjected to hydrothermal treatment at 175 °C for 22-24 h, after cooling to room temperature, the precipitate was filtered, washed with deionized water and ethanol, and dried in a vacuum oven at 60 °C for 12 h to obtain Ce(OH) x nanooctahedron support.
[0011] Further, the Ce(OH) x The nanorod support is prepared by a method comprising the following steps:
[0012] 9 mol / L sodium hydroxide solution was added to 5 mol / L cerium nitrate hexahydrate solution (mass of sodium hydroxide: mass of cerium nitrate hexahydrate = 12.6:1), and stirred vigorously for 30 minutes to form a slurry solution; the mixture was transferred to a Teflon-lined autoclave, and then subjected to hydrothermal treatment at 100 °C for 22-24 h, after cooling to room temperature, the precipitate was filtered, washed with distilled water until the pH was 9.0, and dried in a vacuum oven at 60 °C for 12 h to obtain Ce(OH) x nanorod support.
[0013] Further, the Ce(OH) x The nanocube support is prepared by a method comprising the following steps:
[0014] The 20 mol / L sodium hydroxide solution is added into the 0.08 mol / L cerium nitrate hexahydrate solution (the mass of sodium hydroxide: the mass of cerium nitrate hexahydrate = 86.9:1), and is stirred vigorously for 30 minutes to form a slurry solution; the mixture is transferred into a Teflon-lined autoclave, and then is subjected to hydrothermal treatment at 200 DEG C for 22-24 hours; after cooling to room temperature, the precipitate is filtered, washed with deionized water, and dried in a vacuum oven at 60 DEG C for 12 hours to obtain Ce(OH) x Nanocube carrier.
[0015] Further, the mass of Fe element in the ferric nitrate is 0.25%-10% of the mass of the Ce(OH) x carrier.
[0016] The calcination temperature is 650 DEG C, the holding time is 4 hours, and the heating rate is 5 DEG C / min.
[0017] Application of the iron-based catalyst Fe / CeO2 in a CO2 catalytic hydrogenation reaction.
[0018] The specific steps are as follows:
[0019] Step 1: The iron-based catalyst Fe / CeO2 is placed in a reactor, argon is introduced, and the temperature is raised to 400 DEG C; then the atmosphere is switched to pure hydrogen, and reduction is performed for 1 hour.
[0020] Step 2: After step 1 is completed, the temperature is lowered to 300 DEG C in an argon atmosphere, and a raw gas with a volume ratio of CO2:H2=1:3 is introduced for reaction, and the reaction is performed at 300-600 DEG C.
[0021] The fixed-bed reactor is used as the reverse water gas shift reaction evaluation device. The volume fraction of the raw gas is carbon dioxide (23%), hydrogen (69%), and nitrogen (8%), the catalyst loading is 0.01 g; the reaction temperature is 300-600 DEG C, the space velocity is 400000 mL·g cat -1 ·h -1 .
[0022] The Ce(OH) x The support material is a carrier, which selectively exposes different sections, and based on the strong interaction between the iron nitrate nonahydrate precursor and the surface hydroxyl group, the iron is directly introduced into the Ce(OH) x The Fe / Ce(OH) x material is calcined on the carrier to generate the Fe / CeO2 catalyst and is used in the reverse water gas shift reaction. The Ce(OH) xThe application of octahedral supports promotes the dispersion of iron in the preparation of catalysts. The iron elements highly dispersed on the ceria surface further promote the activation of H2 and the adsorption of CO2 in the RWGS reaction through an association reaction pathway. The CO generation rate of the optimized iron-containing highly dispersed 1Fe / CeO2 octahedral catalyst is 28.99 mmol CO •g Fe -1 •s -1 , and the CO selectivity is 100%. It has high stability when reacted at 600℃ for 150h, and the activity is superior to that of existing non-noble metal catalysts.
[0023] The present application has the following effects:
[0024] (1) The catalyst synthesis method is simple, and the performance is stable. The high dispersion of Fe on the nano-octahedral ceria is realized.
[0025] (2) The catalyst uses a traditional precipitation method to realize good dispersion of the active component, which is conducive to improving the activity, selectivity and stability of the catalyst.
[0026] (3) The catalyst is cheap and has mild synthesis conditions, which is conducive to reducing the production cost of the catalyst and improving the CO yield in the RWGS. BRIEF DESCRIPTION OF DRAWINGS
[0027] Figure 1 The CO2 conversion rate curve of the 0.25%-10% Fe / CeO2 octahedral catalyst prepared in Example 1 of the present application for the RWGS reaction changes with temperature.
[0028] Figure 2 The stability test graph of the 0.25%-10% Fe / CeO2 octahedral catalyst prepared in Example 1 of the present application for the RWGS reaction at 600℃ for 20h.
[0029] Figure 3 The stability test graph of the 1Fe / CeO2 octahedral catalyst prepared in Example 1 of the present application for the RWGS reaction at 600℃ for 150h.
[0030] Figure 4 The TEM photos of the different morphology ceria supports prepared in Example 1 of the present application (Figures a, b and c represent nano-octahedral, nanorod and nanocubic ceria supports, respectively).
[0031] Figure 5Figure 1 shows the Mössbauer spectra of 1.5% Fe supported on cerium oxides of different morphologies prepared in Example 1 of this invention (catalysts supported on octahedral / rod-shaped / cubic cerium oxides are represented as Fe / CeO2-O / R / C, Figure a is the Mössbauer spectrum of the 1.5Fe / CeO2 catalyst, and Figure b is the parameters of the Mössbauer spectrum fitting result).
[0032] Figure 6 The image shows the XRD pattern of the 0.25%-10% Fe / CeO2 catalyst prepared in Example 1 of this invention. Detailed Implementation
[0033] The present invention will be further described below with reference to the accompanying drawings and embodiments.
[0034] Example 1: Preparation of highly dispersed, stable and efficient iron-based RWGS catalyst
[0035] (1) Ce(OH) x Preparation of carrier
[0036] Step 1: Add 1 mol / L sodium hydroxide solution to 5 mol / L cerium nitrate hexahydrate solution and stir vigorously for 30 minutes to form a white slurry. Transfer the mixture to a Teflon-lined autoclave and then perform hydrothermal treatment at 175°C for 24 hours. After cooling to room temperature, filter the precipitate, wash three times with deionized water and ethanol, and dry in a vacuum oven at 60°C for 12 hours to obtain Ce(OH)₂. x Octahedral carrier ( Figure 4 a).
[0037] Step 2: Add 9 mol / L sodium hydroxide solution to 5 mol / L cerium nitrate hexahydrate solution and stir vigorously for 30 minutes to form a slurry. Transfer the mixture to a Teflon-lined autoclave and then perform hydrothermal treatment at 100°C for 24 hours. After cooling to room temperature, filter the precipitate, wash with deionized water until pH 9, and dry in a vacuum oven at 60°C for 12 hours to obtain Ce(OH)₂. x Nanorod support ( Figure 4 b).
[0038] Step 3: Add 20 mol / L sodium hydroxide solution to 0.08 mol / L cerium nitrate hexahydrate solution and stir vigorously for 30 minutes to form a slurry. Transfer the mixture to a Teflon-lined autoclave and then perform hydrothermal treatment at 200°C for 24 hours. After cooling to room temperature, filter the precipitate, wash three times with deionized water and ethanol, and dry in a vacuum oven at 60°C for 12 hours to obtain Ce(OH)₂. x Nanocube carriers ( Figure 4 c).
[0039] (2) Preparation of Fe / Ce02
[0040] Fe / Ce02 catalysts were prepared by deposition-precipitation method.
[0041] The ceria octahedral support was dispersed in deionized water under vigorous stirring. An aqueous solution of iron nitrate nonahydrate (0.01 mol / L) was added dropwise to the suspension. The iron loading was adjusted by the mass of iron nitrate nonahydrate to achieve 0.25%, 0.5wt%, 1%, 1.5%, 3%, 5% and 10wt% iron loading. Sodium carbonate solution (0.57 mol / L) was added to maintain the pH of the suspension at 9.0. The suspension was stirred for 2 h and aged for 2 h. The precipitate was filtered, washed thoroughly with 1 L of deionized water and dried at 60 °C for 12 h. The dried sample was further calcined to 650 °C at a heating rate of 5 °C / min and calcined at 650 °C for 4 h, wherein the loading of Fe on nanorod ceria and nanorod cubic ceria was 1.5%.
[0042] Example 2: Synthesis of syngas by reverse water gas shift reaction catalyzed by Fe / Ce02 catalysts
[0043] The series of catalysts prepared in Example 1 were tested for CO2 catalytic hydrogenation activity in a constant pressure micro fixed bed reactor. Each catalyst (10 mg, 0.2-0.4 mm) was diluted with 2 g of silicon carbide (0.58-0.8 mm) and a K-type thermocouple was inserted into the reactor to measure the temperature of the catalyst. Before the reaction, the catalyst was activated with H2 at 400 °C for 1 h. In the catalytic activity test, a total gas reaction mixture of 66.7 mL / min, of which 23 vol% carbon dioxide, 69 vol% hydrogen and nitrogen balance, corresponding to a GHSV of 400000 mL-g cat -1 ·h -1 . The catalysts were heated to 300 °C, 400 °C, 500 °C and 600 °C, respectively, at a heating rate of 10 °C / min. The effluent gas was monitored by an online mass spectrometer (Agilent 8860) equipped with a thermal conductivity detector (TCD) to stabilize the catalyst. In order to study the stability, the catalytic activity of each catalyst was tracked within 20 h after the activity test of the previous catalyst.
[0044] The calculation formulas of CO2 conversion (formula (1)) and CO selectivity (formula (2)) are as follows:
[0045] CO2 conversion (%) = ([CO2] In - [CO2] Out ) / ([CO2] In ) x 100 (1)
[0046] CO selectivity(%)=([CO] Out ) / ([CO] out +[CH4] Out )×100 (2)
[0047] like Figure 1 and Figure 2 The catalytic performance of the prepared cerium iron oxide octahedral catalyst was evaluated. Before the reaction, the catalyst was activated with H2 at 400 °C for 1 h. In a CO2 / H2 (1:3) gaseous feedstock at a high temperature of 300-600 °C and atmospheric pressure, the space velocity was 400,000 mL·g. cat -1 ·h -1 CO was the only product detected by online gas chromatography during the reaction. Below 400 °C, all iron-cerium dioxide catalysts exhibited low catalytic activity (CO2 conversion <3%). At higher reaction temperatures, CO2 conversion increased with increasing Fe loading, with the highest conversion of 52.26% achieved by Fe / CeO2 with 10 wt% Fe loading. The catalytic activity of the blank cerium support at high temperatures was negligible, with the highest CO2 conversion below 5% at 600 °C. The catalytic activity of the Fe / CeO2 catalysts at 600 °C for 20 h was determined. The catalytic activities of 0.25Fe / CeO2, 0.5Fe / CeO2, and 1Fe / CeO2 remained stable during the reaction. The catalytic activity of the high-loading Fe / CeO2 catalysts decreased slightly, and compared with the currently reported RWGS catalysts, the catalytic activity of the 1Fe / CeO2 catalyst at 600 °C was 28.99 mmol. CO ·g Fe -1 ·s -1 This is significantly higher than the reported iron-based RWGS catalysts (Table 1), and it still exhibits good stability even after extending the reaction time to 150 h at 600 °C. Figure 3 ).
[0048] Ce(OH) nanorods, nanocubes, and nanooctahedrals were prepared using a hydrothermal method. x Carrier material. Based on the strong interaction between the ferric nitrate nonahydrate precursor and surface hydroxyl groups, iron is directly introduced into Ce(OH) via a deposition-precipitation method. x On the support. The prepared Fe / Ce(OH)₂ is then placed... x The material was calcined to produce a Fe / CeO2 catalyst with an iron loading of 1.5 wt%. Mössbauer spectra and parameters are as follows: Figure 5As shown, three components were identified in both Fe / CeO2 rods and Fe / CeO2 cubes. The doublet D1, with an isotropic shift of 0.350 mm / s and a quadrupole split of 1.234 mm / s, can be attributed to iron clusters. The doublet D2, with an isotropic shift of 0.370 mm / s and a lower quadrupole split of 0.736 mm / s, can be attributed to single iron ions, as the greater the chemical bonding of the ions, the larger the isotropic shift. The sextet, with an isotropic shift between 0.372 and 0.380 mm / s and a quadrupole split between -0.206 and -0.237 mm / s, and a magnetic field of 50.90 T, can be attributed to larger Fe2O3 nanoparticles (greater than 10 nm). In the Fe / CeO2 octahedral sample, only Fe single ions and clusters were identified, indicating a strong interaction between the support and the metal and that Fe can be highly dispersed during the loading process on the cerium oxide octahedral support. In order to optimize the catalytic performance of the RWGS reaction and further understand the catalytic active sites, Fe / CeO2 octahedral catalysts with different iron loads were further studied.
[0049] like Figure 6 As shown, distinct XRD peaks were observed at 2θ = 28.46°, 33.01°, 47.39°, 56.29°, 59.05°, 69.34°, 76.69°, and 79.01° for both CeO2 and Fe / CeO2 catalysts, which are attributed to the cubic fluorite structure of CeO2 (PDF#43-1002). The variation in diffraction peak positions was negligible. No ferrous oxide, ferric oxide, or magnetite phases were detected, indicating that iron atoms are either incorporated into the cerium lattice or exist as ultrasmall iron oxide particles within the detection limit.
[0050]
Claims
1. A method for preparing an iron-based catalyst Fe / CeO2, characterized in that: Ce(OH) x The support was dispersed in deionized water under stirring, then the aqueous solution of iron nitrate nonahydrate was added dropwise, the loading of iron was adjusted by the mass of iron nitrate nonahydrate added, the pH value of the system was adjusted to 9.0 by adding sodium carbonate solution, stirring for 2 h, aging for 2 h; the precipitate was filtered, washed with deionized water, and continuously dried at 60°C for 12 h, and the dried sample was further calcined to obtain the iron-based catalyst Fe / CeO2; the calcination temperature is 650℃, the holding time is 4h, and the heating rate is 5℃ / min; Ce(OH) x The morphology of the support includes one or more of Ce(OH) x nano-octahedron support, Ce(OH) x nanorod support, Ce(OH) x nanocube support, Ce(OH) said Ce(OH) x The nano-octahedral support is obtained by a method comprising the steps of: A solution of sodium hydroxide was added to a solution of cerium nitrate hexahydrate, stirred to form a white slurry solution; the mixture was transferred to a Teflon lined autoclave and then subjected to hydrothermal treatment at 175 °C for 22-24 h, after cooling to room temperature, the precipitate was filtered, washed with deionized water and ethanol, and vacuum dried to obtain Ce(OH) x nano-octahedral support; the Ce(OH) x The nanorod support is prepared by a method comprising the steps of: A solution of sodium hydroxide was added to a solution of cerium nitrate hexahydrate, and the mixture was stirred to form a slurry. The slurry was transferred to a Teflon-lined autoclave and then subjected to hydrothermal treatment at 100°C for 22-24 hours. After cooling to room temperature, the precipitate was filtered, washed with distilled water until the pH was 9.0, and dried under vacuum to obtain Ce(OH) x nanorod supports; said Ce(OH) x The nanocube carriers are prepared by a method comprising the steps of: A solution of sodium hydroxide was added to a solution of cerium nitrate hexahydrate, and the mixture was stirred to form a slurry. The slurry was transferred to a Teflon-lined autoclave and then subjected to hydrothermal treatment at 200°C for 22-24 hours. After cooling to room temperature, the precipitate was filtered, washed with deionized water, and vacuum dried to obtain Ce(OH) x nanocube carriers.
2. The method according to claim 1, characterized in that: the Ce(OH) x The morphology of the support is Ce(OH) x Nanooctahedral support.
3. The method according to claim 1, characterized in that: The mass of Fe element in the ferric nitrate is 0.5%-2% of the mass of Ce(OH) x 0.25%-10% of the mass of the carrier.
4. The application of the iron-based catalyst Fe / CeO2 prepared by the method according to any one of claims 1-3 in a CO2 catalytic hydrogenation reaction.
5. Use according to claim 4, characterized in that including the following steps: Step 1: Put the iron-based catalyst Fe / CeO2 into a reactor, first pass in argon and heat to 400℃, switch to pure hydrogen atmosphere reduction for 1h; Step 2: After step 1, cool to 300℃ in argon atmosphere, pass in raw gas with a volume ratio of CO2:H2=1:3, and react at 300-600℃.