Catalyst with gradient oxygen defect distribution as well as preparation method and application of catalyst

Abstract

The invention discloses a gradient oxygen defect distribution catalyst and a preparation method and application thereof, the catalyst is A2Ce (2-x) MxO7-delta composite oxide, the element A is selected from any one of La, Sm, Pr, Gd, Pr and Nd; the element M is selected from any one of Ca, Mg, Sr, Ba, Fe, Co and Mn, the value range of x is 0.1-0.4, and delta is an oxygen non-stoichiometric value; the oxygen vacancy concentration of the catalyst is distributed in a gradient decreasing mode from the surface layer of the particle to the interior of the bulk phase, and the oxygen vacancy concentration of the surface layer is 1.5 times or above that of the interior of the bulk phase. The structure is constructed through a two-stage programmed heating reduction method, wherein surface layer high defects are formed at the low temperature and the low hydrogen concentration, and then the gradient extends towards the interior of a bulk phase at the high temperature and the high hydrogen concentration. The gradient structure synergistically improves the catalytic activity and the anti-carbon deposition stability, in a diesel steam reforming hydrogen production reaction, the hydrogen yield exceeds 70%, the carbon deposition amount is significantly lower than that of a traditional homogeneous catalyst, and the industrial problem that activity and stability are difficult to consider is effectively solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalysts for hydrogen production by steam reforming of heavy hydrocarbon fuels, in particular to a catalyst with gradient oxygen defect distribution and its preparation method and application. BACKGROUND

[0002] Hydrogen energy is considered as the core of future energy system due to its cleanliness and high efficiency. However, the high cost of hydrogen storage and transportation seriously restricts its large-scale application. Using diesel, which has perfect existing infrastructure and high-quality hydrogen density (about 13.0wt%), as a mobile or distributed hydrogen production raw material is a promising technical route.

[0003] However, diesel has complex components. In the reforming reaction process, traditional supported catalysts (such as Ni-based catalysts with CeO2, MgO and Al2O3 oxides as carriers) face the fundamental contradiction that high activity and high stability cannot be reconciled. To achieve high activity, it is usually necessary to create abundant active sites, for example, by introducing oxygen vacancies through doping in cerium-based materials. However, existing technologies generally pursue the construction of uniformly distributed high-concentration oxygen vacancies in the bulk phase of the catalyst through homogeneous doping. This strategy has two fatal defects: First, the existing doping strategy forms uniformly distributed oxygen vacancies throughout the catalyst (from the surface to the bulk phase). A large number of oxygen vacancies will destroy the integrity of the crystal structure of the catalyst body, causing the catalyst body to collapse during high-temperature reaction, resulting in a significant decrease in stability. Second, the localized electrons formed by oxygen vacancies can act as Lewis base sites, bind with hydrocarbon molecules (Lewis acids) and initiate chemical adsorption, and ultimately form carbon deposition during the subsequent dehydrogenation process. In existing solutions, bulk oxygen vacancies will become "deep carbon deposition sites"---the adsorbed carbon species will diffuse from the catalyst surface to the bulk phase and deposit, forming deep carbon deposition that is difficult to remove, further shortening the service life of the catalyst.

[0004] In summary, existing diesel reforming hydrogen production catalysts cannot simultaneously meet the needs of "high activity" (requiring sufficient oxygen vacancies) and "high stability" (requiring structural integrity and no deep carbon deposition), and there is an urgent need for a new catalyst design strategy that can synergistically regulate oxygen vacancy distribution and balance activity and stability. SUMMARY

[0005] The present application aims to overcome the shortcomings of the prior art and provide a catalyst with gradient oxygen defect distribution and its preparation method and application. The catalyst aims to gradually decrease the oxygen vacancy concentration from the surface to the bulk phase, allowing the high-concentration oxygen vacancies on the surface to ensure high reactivity, while the low-defect concentration in the bulk phase maintains structural stability and inhibits the growth of carbon deposition inside, ultimately solving the fundamental contradiction between high activity and high stability in the reforming of heavy hydrocarbon fuels (such as diesel) for hydrogen production.

[0006] To achieve the above objectives, the specific solution adopted by the present invention is as follows: On one hand, the present invention provides a catalyst with a gradient oxygen defect distribution, characterized in that the catalyst is A2Ce. 2-x M x O 7-δ A composite oxide, wherein element A is selected from any one of La, Sm, Pr, Gd, Pr, and Nd; element M is selected from any one of Ca, Mg, Sr, Ba, Fe, Co, and Mn; the value of x ranges from 0.1 to 0.4; and δ is the non-stoichiometric value of oxygen. The oxygen vacancy concentration of the catalyst decreases in a gradient from the surface of the particle to the interior of the bulk phase, wherein the oxygen vacancy concentration at the surface is more than 1.5 times that at the interior of the bulk phase.

[0007] Furthermore, the surface of the catalyst satisfies the condition that the ratio of defect oxygen to the sum of defect oxygen and bulk oxygen is greater than 60%.

[0008] The bulk condition is satisfied that the ratio of defect oxygen to the sum of defect oxygen and bulk oxygen is less than 30%.

[0009] On the other hand, the present invention provides a method for preparing a catalyst with gradient oxygen defect distribution, wherein the catalyst can be obtained by treating the precursor in the following three stages: First stage: Treat for 1-3 hours at a temperature of 400-550℃ and a reducing atmosphere with an H2 volume fraction of 3-15% to promote the generation of high-concentration oxygen defects on the surface. The second stage involves treating the sample for 0.5-2 hours at a temperature of 600-750℃ and in a reducing atmosphere with a volume fraction of 10-20% H2, allowing the reduction to diffuse into the bulk phase and thus form an oxygen defect concentration gradient. The third stage: cooling to room temperature in an inert atmosphere to eliminate surface dangling bonds.

[0010] Furthermore, the precursor is prepared by the sol-gel method, specifically including the following steps: (1) Dissolve the metal salt, complexing agent and crosslinking agent in water to form a mixed solution, and heat in a water bath at 60-80℃ to form a hydrogel; (2) The hydrogel is dried at 110-130℃ to obtain a net-like fluffy solid; (3) After grinding the net-like fluffy solid, calcining it at 800-900℃ for 4-6 hours, the precursor can be obtained.

[0011] Furthermore, the metal precursor comprises nitrates of A, Ce, and M; and / or; The complexing agent is citric acid monohydrate; and / or; The crosslinking agent is ethylene glycol.

[0012] In another aspect, the present invention provides the application of the above-mentioned catalyst in the hydrogen production reaction of heavy hydrocarbon fuel steam reforming.

[0013] Furthermore, the heavy hydrocarbon fuel is diesel or biofuel.

[0014] Furthermore, the feed gas for the reforming reaction is a mixture of heavy hydrocarbon fuel and steam, wherein the water-to-carbon molar ratio is 2-4:1.

[0015] Furthermore, the reforming reaction is carried out in a catalyst bed at a temperature of 650~850℃.

[0016] This invention successfully resolves the fundamental contradiction of simultaneously achieving high activity and high stability by constructing a gradient distribution of oxygen vacancies. Its beneficial effects are specifically reflected in: (1) The catalyst of the present invention has a high concentration of oxygen vacancies on its surface. These oxygen vacancies, as Lewis base sites, can effectively activate CH bonds and dissociate water molecules, thus ensuring the high activity of the reforming reaction of heavy hydrocarbon fuels (such as diesel).

[0017] (2) The catalyst of the present invention maintains a low defect concentration in the bulk phase, which maintains the stability of the catalyst bulk crystal structure and prevents the framework collapse caused by excessive reduction of the bulk phase. More importantly, this gradient structure of "defect-rich surface and defect-poor bulk phase" effectively inhibits the growth of carbon deposits. The oxygen vacancies on the surface are used for catalytic reaction, while the low-defect region inside cuts off the channels for carbon species to penetrate and deposit into the catalyst, avoiding the formation of deep carbon deposits, thereby significantly improving the catalyst lifetime.

[0018] (3) By adjusting the types of A (rare earth elements) and M (doping elements) and the gradient reduction process parameters (temperature, H2 concentration, time), the present invention can reliably and repeatedly construct the required gradient oxygen defects on A2Ce2O7 based materials with different compositions. The process is highly versatile and easy to scale up.

[0019] (4) The present invention prepares the precursor by sol-gel method, which ensures that the metal ions in the precursor are uniformly dispersed; the two-stage gradient reduction can precisely control the distribution gradient of oxygen vacancies, avoiding the problem of uncontrollable oxygen vacancies distribution in the existing process.

[0020] (5) The catalyst is suitable for various heavy hydrocarbon fuels such as diesel and bio-oil, and the reaction conditions (water-to-carbon ratio 2~4:1, temperature 650~850℃) are compatible with existing industrial reforming units, without the need for large-scale modification of existing equipment. Attached Figure Description

[0021] Figure 1 XPS spectra of the Ce 3d and O 1s surface and bulk phases of the product obtained in Example 1.

[0022] Figure 2 O is the product obtained in Example 1 V / (O V +O L The curve showing the change of the value with the sputtering depth. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0024] This invention provides a catalyst with gradient oxygen defect distribution, its preparation method and application. The core is to achieve the synergy between catalyst surface activity and bulk stability through "gradient oxygen vacancy design" and "controllable gradient reduction process".

[0025] Secondly, the present invention provides a catalyst, wherein the catalyst is A2Ce. 2-x M x O 7-δ The composite oxide comprises: A, a trivalent rare earth element selected from La, Sm, Pr, Gd, Pr, and Nd; M, a dopant element selected from alkaline earth metals (Ca, Sr) or transition metals (Fe, Cu, Mn); x, the doping amount, ranging from 0.1 to 0.4; and δ, the oxygen nonstoichiometry value, reflecting the number of oxygen vacancies, which decreases gradually from the catalyst particle surface to the bulk phase. The oxygen vacancy concentration decreases gradually from the catalyst particle surface to the bulk phase, with the oxygen vacancy concentration on the surface being more than 1.5 times that in the bulk phase.

[0026] Furthermore, the catalyst surface satisfies the following conditions: the ratio of defect oxygen to the sum of defect oxygen and bulk oxygen is greater than 60%, ensuring high surface activity. The bulk phase satisfies the following condition: the ratio of defect oxygen to the sum of defect oxygen and bulk oxygen is less than 30%, maintaining bulk structural stability.

[0027] Secondly, the present invention provides a method for preparing the above-mentioned catalyst, wherein the catalyst is prepared in two steps: "precursor preparation (sol-gel method) + gradient reduction heat treatment", and each step is described in detail below.

[0028] S1. Preparation of precursors (sol-gel method) S11. Preparation of mixed aqueous solution: Prepare a mixed aqueous solution by mixing nitrates of elements corresponding to A, Ce, and M (such as La(NO3)3·6H2O, Ce(NO3)3·6H2O, and Ca(NO3)2·4H2O), and add a complexing agent (citric acid monohydrate) to the solution; place the mixed solution in a water bath at 60~80℃, then add a crosslinking agent (ethylene glycol), and heat for 3~5 hours until a transparent hydrogel is formed. The purpose of this step is to achieve uniform dispersion of metal ions by coordinating the complexing agent with the metal ions and promoting the esterification reaction through the crosslinking agent. S12. Drying treatment: The hydrogel obtained in step S11 is placed in an oven at 110~130℃ and dried to obtain a net-like fluffy solid. The purpose of this step is to remove the water in the hydrogel, retain the uniform metal-organic framework structure, and avoid particle agglomeration during subsequent calcination. S13. Calcination treatment: After grinding the loose, reticulated solid obtained in step S12, place it in a muffle furnace and heat it to 800-900℃ at a heating rate of 2-5℃ / min, calcining for 4-6 hours to obtain the precursor. The purpose of this step is to remove organic components (citric acid, ethylene glycol) through high-temperature calcination, allowing the metal ions to form a stable A2Ce2O7-based composite oxide crystal structure. S2. Gradient reduction heat treatment (constructing gradient oxygen vacancies): To obtain a catalyst with a gradient oxygen defect distribution, the precursor obtained in step S13 is placed in a reactor and subjected to a two-stage temperature-programmed reduction treatment and a final cooling treatment, as detailed below: S21, Low-temperature, low-concentration reduction: Treatment at a low temperature (400~550℃) and a low reducing gas concentration (3~15% H2 / Ar, volume fraction) for 1~3 hours. This step promotes the formation of high-concentration oxygen vacancies on the surface. Under these mild conditions, the reduction reaction occurs only on the catalyst surface, resulting in a high concentration of Ce on the surface. 4+ Partially restored to Ce 3+ It generates a high concentration of oxygen vacancies without affecting the bulk structure; S22, High-Temperature, High-Concentration Reduction: This is followed by treatment at a relatively high temperature (600~750℃) and a relatively high reducing gas concentration (10~20% H2 / Ar, volume fraction) for 0.5~2 h. This step allows the reduction to slowly diffuse into the catalyst bulk phase, from the surface to the bulk Ce... 4+ The degree of reduction gradually decreases, forming a gradient distribution of oxygen vacancy concentration from the surface to the bulk phase; S23. Cooling Stabilization: Cool to room temperature in an inert atmosphere (such as N2 or Ar). The purpose of this step is to eliminate surface dangling bonds, stabilize the gradient structure, and prevent the unstable surface structure at high temperatures from relaxing or changing during the cooling process.

[0029] Thirdly, the present invention provides the application of the above-mentioned catalyst. The A2Ce with the gradient oxygen defect distribution... 2- x M x O 7-δ The catalyst is used in the steam reforming of diesel, bio-oil, or other heavy hydrocarbon fuels for hydrogen production. Specific application conditions include: Raw material: n-hexadecane containing dibenzothiophene was used as simulated diesel fuel (simulating the aromatic and sulfide components in actual diesel fuel). Water-to-carbon ratio: The water-to-carbon molar ratio in the feed gas is 2~4:1, preferably 3:1 (to ensure sufficient H2O to participate in the reaction and inhibit carbon deposition). Reaction temperature: 650~850℃ (to ensure complete cracking and reforming of diesel molecules); Reaction method: The mixture of diesel and water is vaporized and then contacted with a catalyst bed for reforming reaction to generate high concentration of H2.

[0030] The present invention is further illustrated below with specific embodiments and comparative examples, but these do not limit the scope of protection of the present invention. All raw materials used in the embodiments are commercially available analytical grade reagents and have not undergone special treatment.

[0031] Example 1 (La2Ce) 1.8 Ca 0.2 O 7-δ (Preparation of catalysts) S1. Precursor Preparation S11. Accurately weigh 2 parts of lanthanum nitrate hexahydrate (La(NO3)3·6H2O), 1.8 parts of cerium nitrate hexahydrate (Ce(NO3)3·6H2O), and 0.2 parts of calcium nitrate tetrahydrate (Ca(NO3)2·4H2O) in molar amounts, add them to 5 mL of deionized water to prepare a 0.5 M mixed solution, and place it in an 80℃ water bath. S12, then accurately weigh 4.8 parts of citric acid monohydrate (C6H) 10 O8) and 4.8 parts of ethylene glycol ((CH2OH)2) were added to the mixed solution, stirred and heated for 4 hours until the water evaporated to form a transparent hydrogel; S13. Dry the hydrogel in an oven at 130℃ to obtain a loose, net-like solid. S14. After grinding the solid, place it in a muffle furnace and heat it to 900°C at a heating rate of 5°C / min. Calcine for 4 hours to obtain the precursor. S2, Gradient reduction heat treatment The above precursor was placed in a reactor and subjected to the following treatment: Treat for 2 hours under an atmosphere of S21, 500℃, and 5% H2 / Ar (volume fraction); Treat for 1 hour under an atmosphere of S22, 650℃, and 15% H2 / Ar (volume fraction); S23. After the reaction is complete, the mixture is cooled to room temperature under nitrogen protection to obtain La2Ce with a gradient oxygen vacancy distribution. 1.8 Ca 0.2 O 7-δ catalyst.

[0032] Example 2 (Sm2Ce) 1.9 Fe 0.1 O 7-δ (Preparation of catalysts) S1. Precursor Preparation S11. Accurately weigh 2 parts of samarium nitrate hexahydrate (Sm(NO3)3·6H2O), 1.9 parts of cerium nitrate hexahydrate (Ce(NO3)3·6H2O), and 0.1 parts of ferrous nitrate nonahydrate (Fe(NO3)2·9H2O) in molar amounts, add them to 5 mL of deionized water to prepare a 0.5 M mixed solution, and place it in a 60 °C water bath. S12, then add 4.8 parts of citric acid monohydrate and 4.8 parts of ethylene glycol, stir and heat for 5 hours to form a transparent hydrogel; S13. The hydrogel was dried in an oven at 110°C to obtain a loose, net-like solid. S14. After grinding the solid, heat it in a muffle furnace to 800℃ at 2℃ / min and calcine it for 6h to obtain the precursor. S2, Gradient reduction heat treatment The precursor was placed in a reactor and subjected to the following treatment: Treatment at S21, 400℃, 3% H2 / Ar (volume fraction) atmosphere for 1.5h; Treat for 1 hour under an atmosphere of S22, 600℃, and 10% H2 / Ar (volume fraction); S23, cooled to room temperature under nitrogen protection, yields Sm2Ce with gradient oxygen defect distribution. 1.9 Fe 0.1 O 7-δ catalyst.

[0033] Comparative Example 1 (uniform oxygen vacancies La2Ce) 1.8 Ca 0.2 O 7-δ -1 Preparation of catalyst) The precursor prepared in Example 1 was placed in a reactor and reduced at 650°C for 2 hours under a 5% H2 / N2 (volume fraction) atmosphere. After cooling to room temperature, La2Ce with uniform oxygen vacancy distribution was obtained. 1.8 Ca 0.2 O 7-δ -1 catalyst (no gradient distribution).

[0034] The performance of the products obtained in Examples 1-2 and Comparative Example 1 will be tested and the results analyzed.

[0035] First, tests on conversion rate, hydrogen production, and carbon deposition. 1. Testing Method The performance of the catalysts in Examples 1-2 and Comparative Example 1 for hydrogen production via diesel steam reforming was tested. The specific methods are as follows: (1) Raw material vaporization: Hexadecane containing dibenzothiophene (simulated diesel) is mixed with water at a water-to-carbon molar ratio of 3:1 and transported to the pipeline by a high-pressure liquid phase pump. N2 is used as the carrier gas to carry it into the 300°C vaporization chamber for full vaporization and mixing. (2) Reforming reaction: The vaporized raw material gas enters the reactor and contacts the catalyst bed to carry out the reforming reaction at a temperature of 800℃. (3) Product detection: The reformed product is first separated into gas and liquid phases by a condenser, and the main gas phase enters an online gas chromatograph to detect the contents of N2, H2, CO, CO2 and CH4; (4) Evaluation indicators: Continuous evaluation for 30 hours, calculate diesel conversion rate, hydrogen production and carbon deposit amount, the calculation formula is as follows: (a) Diesel conversion rate (%): ; Where, n(C) 16 H 34 ) out n(C) represents the amount of substance output by diesel fuel. 16 H 34 ) in This represents the amount of diesel fuel input. The conversion rate formula reflects the degree of diesel fuel consumption. (b) Hydrogen production (%): ; Where n(H2) represents the amount of H2, n(CH4) represents the amount of CH4, n(CO) represents the amount of CO, and n(CO2) represents the amount of CO2. This formula reflects the proportion of H2 in the gaseous products; (c) Carbon deposit amount (g) carbon / g catalyst After the reaction is complete, the mass of carbon deposits on the catalyst after use is determined by thermogravimetric analysis (TGA) and divided by the mass of the catalyst.

[0036] 2. Test Results The products of Examples 1-2 and Comparative Example 1 were tested according to the above method, and the test results are shown in Table 1.

[0037] Table 1 Test Results As shown in Table 1, the catalysts of Examples 1 and 2 maintained a conversion rate of nearly 100% and a hydrogen yield of approximately 70% after 30 hours of reaction, significantly better than Comparative Example 1. This demonstrates the decisive role of high surface oxygen vacancies in reaction activity. Meanwhile, the carbon deposition in Examples 1 and 2 (approximately 0.13) was much lower than that in Comparative Example 1 (1.2), a difference of nearly an order of magnitude. This strongly confirms the significant advantage of gradient oxygen defect structures in suppressing carbon deposition, particularly preventing deep carbon deposition.

[0038] Second, analyze the oxygen vacancy concentration using the attached diagram. Figure 1 These are XPS spectra of the Ce 3d and O 1s surface and bulk phases of the product from Example 1. As shown in the figure, in the Ce 3d spectrum (left image), the Ce in the surface region... 3+ The characteristic peak intensity is significantly higher than that of the bulk phase, and the surface Ce 3+ / (Ce 3+ +Ce 4+ The ratio was 34.1%, while the bulk concentration was only 15.5%, which proves that the surface Ce... 4+ Higher degree of reduction, generating more Ce 3+ This corresponds to a higher oxygen vacancy concentration. In the O1s spectrum (right figure), the characteristic peak intensity of defect oxygen in the surface region is much higher than that in the bulk phase. On the surface of the catalyst, the ratio of defect oxygen to the sum of surface defect oxygen and bulk oxygen is 62.5% (>60%), while in the bulk phase of the catalyst, the ratio is 25.5% (<30%). This directly verifies the high concentration of oxygen vacancies on the surface and the low concentration in the bulk phase, which is consistent with the gradient design of this invention.

[0039] Figure 2 For the product of Example 1, O V / (O V +O L The curve shows the change of O value with sputtering depth. As the sputtering depth increases from 0 nm to 20 nm, it corresponds to penetration from the catalyst surface into the bulk phase. With increasing sputtering depth, O... V / (O V +O L The value gradually decreased from greater than 60% to less than 30%, also showing a gradient decrease. This proves that the oxygen vacancy concentration (composed of O...) V / (O V +O LThe oxygen vacancy rate indirectly reflects the decreasing gradient from the catalyst surface to the bulk phase. This gradient distribution is the core reason for the high activity and low carbon deposition of Example 1. Compared with the uniform oxygen vacancies in Comparative Example 1, the gradient distribution ensures both surface activity and avoids bulk structure damage and deep carbon deposition. It should be noted that due to equipment limitations in argon ion sputtering technology for XPS depth profiling analysis, the depth range of this test was limited to 0-20 nm. However, considering the preparation principle of this catalyst—that the driving force of temperature-programmed reduction gradually weakens from the surface to the interior—it can be reasonably inferred that the degree of reduction is lower in deeper regions of the bulk phase (e.g., >20 nm). Therefore, the ratio of defect oxygen to the sum of bulk oxygen in deeper regions is expected to be less than 30%, and may even be further reduced, ensuring the overall stability of the catalyst's bulk structure.

[0040] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention in any way. All equivalent transformations or modifications made in accordance with the essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A catalyst with a gradient oxygen defect distribution, characterized in that, The catalyst is A2Ce. 2-x M x O 7-δ A composite oxide, wherein element A is selected from any one of La, Sm, Pr, Gd, Pr, and Nd; element M is selected from any one of Ca, Mg, Sr, Ba, Fe, Co, and Mn; the value of x ranges from 0.1 to 0.4; and δ is the non-stoichiometric value of oxygen. The oxygen vacancy concentration of the catalyst decreases in a gradient from the surface of the particle to the interior of the bulk phase, wherein the oxygen vacancy concentration at the surface is more than 1.5 times that at the interior of the bulk phase.

2. The catalyst according to claim 1, characterized in that, The surface of the catalyst satisfies the following condition: the ratio of defect oxygen to the sum of defect oxygen and bulk oxygen is greater than 60%. The bulk condition is satisfied that the ratio of defect oxygen to the sum of defect oxygen and bulk oxygen is less than 30%.

3. A method for preparing a catalyst with gradient oxygen defect distribution according to any one of claims 1-2, characterized in that, The catalyst can be prepared by processing the precursor in the following three stages: First stage: Treat for 1-3 hours at a temperature of 400-550℃ and a reducing atmosphere with an H2 volume fraction of 3-15% to promote the generation of high-concentration oxygen defects on the surface. The second stage involves treating the sample for 0.5-2 hours at a temperature of 600-750℃ and in a reducing atmosphere with a volume fraction of 10-20% H2, allowing the reduction to diffuse into the bulk phase and thus form an oxygen defect concentration gradient. The third stage: cooling to room temperature in an inert atmosphere to eliminate surface dangling bonds.

4. The method as described in claim 3, characterized in that, The precursor is prepared by the sol-gel method, specifically including the following steps: (1) Dissolve the metal salt, complexing agent and crosslinking agent in water to form a mixed solution, and heat in a water bath at 60-80℃ to form a hydrogel; (2) The hydrogel is dried at 110-130℃ to obtain a net-like fluffy solid; (3) After grinding the net-like fluffy solid, calcining it at 800-900℃ for 4-6 hours, the precursor can be obtained.

5. The method as described in claim 4, characterized in that, The metal precursor comprises nitrates of A, Ce, and M; and / or; The complexing agent is citric acid monohydrate; and / or; The crosslinking agent is ethylene glycol.

6. The application of the catalyst as described in any one of claims 1-2 in the hydrogen production reaction of heavy hydrocarbon fuel steam reforming.

7. The application according to claim 6, characterized in that, The heavy hydrocarbon fuel is diesel or biofuel.

8. The application as described in claim 6, characterized in that, The feed gas for the reforming reaction is a mixture of heavy hydrocarbon fuel and steam, wherein the water-to-carbon molar ratio is 2-4:

1.

9. The application as described in claim 6, characterized in that, The reforming reaction is carried out in a catalyst bed at a temperature of 650-850°C.

Images