Supported catalyst Ptluster / LaCeO2 as well as preparation method and application thereof

Abstract

The invention provides a doped catalyst Pt / La-CeO2 as well as a preparation method and application thereof, and solves the technical problems of complex preparation process and low methane hydrogen production efficiency of the existing methane reforming hydrogen production reaction catalyst. According to the method, a nanorod Ptcluster / La-CeO2 catalyst uniform in morphology is prepared through a simple two-step hydrothermal method and a photo-assisted deposition method firstly, then a reaction is carried out in a mixed atmosphere (10 mL min <-1 > CH4, 15 mL min <-1 > N2 and 40 mL min <-1 > H2O), at the temperature of 500 DEG C, the CH4 conversion rate reaches up to 54.4% and is close to the equilibrium conversion rate (55.6%) at the moment, and the CH4 hydrogen production efficiency reaches up to 3.90 mol H2mol CH4 <-1 >.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal catalysis, and particularly relates to a supported catalyst Pt cluster / LaCeO 2 and its preparation method and application in low-temperature methane steam reforming. Background Art

[0002] With the development of industry, people's demand for hydrogen energy has been increasing. As of 2024, the demand for hydrogen energy has reached 100 million tons. At present, hydrogen production by methane steam reforming is an important source of industrial hydrogen production. There is a huge price difference between methane and water. Therefore, consuming less methane to produce more hydrogen is more economically promising. However, due to the chemical inertness of methane, a higher temperature is beneficial to promoting methane activation for reaction. However, too high reaction temperature will cause by-product CO to be more easily desorbed, which thermodynamically limits the hydrogen production efficiency of methane. Therefore, only at low temperatures can a high methane hydrogen production efficiency be expected. At present, the reaction temperature of methane steam reforming is relatively high, and the methane hydrogen production efficiency needs to be improved. In addition, the catalysts used in methane steam reforming are also often deactivated easily at high temperatures, and there are problems such as difficulty in balancing high activity and high hydrogen selectivity. For example, the Ni / Al 2 O 3 catalyst used in industry has achieved methane steam reforming at high temperature (>700 °C), but has not solved the problem of low methane hydrogen production efficiency (10.1016 / j.ijhydene.2018.12.112.). Therefore, how to overcome the chemical inertness of methane and activate methane at low temperatures is the key scientific problem for realizing low-temperature methane steam reforming.

[0003] In view of this, the research team of the present invention believes that it is necessary to design a catalyst with a simple preparation process, capable of balancing high activity and high hydrogen selectivity for low-temperature methane steam reforming, so as to solve the problem of low methane hydrogen production efficiency. Summary of the Invention

[0004] The purpose of the present invention is to solve the technical problems that in the current hydrogen production by methane steam reforming, the catalyst is easily deactivated at high temperatures, it is difficult to balance high activity and high hydrogen selectivity, and the methane hydrogen production efficiency is relatively low, and to provide a supported catalyst Pt cluster / LaCeO 2 and its preparation method and application in low-temperature methane steam reforming.

[0005] The concept of the present invention:

[0006] The chemical equation for hydrogen production by methane steam reforming is: CH 4 +2H 2 O→CO 2 +4H 2 ; The side reaction is: CH4 +H 2 O → CO + 3H 2 ; In view of the problems existing in the current catalysts for hydrogen production by low-temperature methane steam reforming, the research team of the present invention considered that in the design of catalysts for hydrogen production by low-temperature methane steam reforming, the following points need to be met:

[0007] 1) It can effectively activate small molecule H 2 O and convert it into *H and *OH intermediates, providing the possibility for further WGS reaction;

[0008] 2) Avoid the generation and desorption of by-product CO, which causes low hydrogen production efficiency of methane and limits its application in hydrogen production by low-temperature methane steam reforming.

[0009] Therefore, combining the design requirements of catalysts for hydrogen production by low-temperature methane steam reforming and the current bottlenecks, the research team intends to use the idea of dual-site activation. The surface of CeO 2 has unique and abundant oxygen vacancies, which can effectively activate H 2 , CO 2 , H 2 O and other small molecules. By introducing La, the oxygen vacancy formation energy is reduced, the oxygen vacancy concentration is increased, and the activation of H 2 O is further enhanced; in addition, CH 4 is easily activated by Pt; therefore, the research team of the present invention intends to prepare a supported catalyst Pt cluster / LaCeO 2 , using noble metal Pt and carrier LaCeO 2 to activate the substrate simultaneously and realize the application of a bifunctional catalyst. At present, some morphologies of CeO 2 have abundant oxygen vacancies, but the oxygen vacancy formation energy is relatively high, which hinders the direct utilization of the existing CeO 2 . In addition, the preparation process of CeO 2 with abundant oxygen vacancies is cumbersome, or additional oleylamine and the like need to be added, resulting in a complex sample post-treatment process and some impurity residues, making it difficult to establish a structure-activity relationship between the catalytic activity and structure of CeO 2 . Therefore, the research team of the present invention optimized the preparation process of CeO 2 , first prepared La-doped CeO 2 (i.e., LaCeO 2 ), and then loaded Pt on its surface in the form of clusters to form a supported catalyst Pt cluster / LaCeO 2 , to solve the problem of low methane hydrogen production efficiency in methane steam reforming for hydrogen production.

[0010] Based on the above inventive concept, to achieve the above object, the technical solution provided by the present invention is:

[0011] A supported catalyst Pt cluster / LaCeO 2 The preparation method is characterized in that it includes the following steps:

[0012] 1) In the cooled strong base solution, dropwise add the solution prepared from Ce salt, La salt and ultrapure water, and prepare LaCe(OH) 3 / CeO 2 precursor;

[0013] 2) Ultrasonically disperse the LaCe(OH) 3 / CeO 2 precursor obtained in step 1) in ultrapure water, and then obtain the porous rod-shaped support LaCeO 2 by hydrothermal method under high pressure;

[0014] 3) Load platinum on the support LaCeO 2 obtained in step 2) by photo-assisted deposition, and reduce it in the atmosphere of argon and hydrogen to obtain the supported catalyst Pt cluster / LaCeO 2 , wherein the loading amount of Pt is greater than 0.2 wt% and less than 1.5 wt%, that is, the mass ratio of Pt to LaCeO 2 ; it can be measured by the test results of ICP-OES / MS that only when the loading amount of Pt is within this range can it exist in the form of clusters and exert the expected activation effect; while the loading amount of La is 2-7 wt%.

[0015] Furthermore, step 1) is specifically:

[0016] Slowly add a strong base (as a precipitant in the co-precipitation method) to a glass bottle filled with ultrapure water, stir, and after the strong base solution cools, slowly dropwise add the solution prepared from Ce(NO 3 ) 3 ·6H 2 O, La(NO 3 ) 3 ·6H 2 O and ultrapure water (in order to reduce the influence of other impurity ions, nitrates are used here to avoid the influence caused by introducing other anions), stir at room temperature after dropping, and place it in a glass bottle and react at 100-120 °C for 12-24 h (the reaction temperature cannot be too high, otherwise it will affect the content of Ce(OH) 3 , preferably react at 100 °C for 24 h), after the reaction is completed, wash it alternately with water and alcohol for multiple times, and then dry it at 60-80 °C for 8-12 h to obtain La-Ce(OH) 3 / CeO 2Precursor

[0017] Further, in step 1), the strong base is a strong base such as NaOH or KOH; the molar concentration of OH - in the reaction solution is 2 - 6 mol / L (i.e., after adding the strong base solution to the solution prepared from Ce(NO 3 ) 3 ·6H 2 O, La(NO 3 ) 2 ·6H 2 O and ultrapure water, the molar concentration of OH - is 2 - 6 mol / L);

[0018] The molar ratio of La to Ce is 1:10 - 50 (preferably 1:20), and the molar concentration of Ce in the reaction solution is 40 - 60 mmol / L; thus, the concentration of OH - is above 1 M, and the concentration is one order of magnitude higher than that of Ce, which is beneficial to the formation of Ce(OH) 3 and lays the foundation for subsequent reconstruction.

[0019] Further, in step 2), the La - Ce(OH) 3 / CeO 2 precursor is ultrasonically dispersed in ultrapure water at an addition ratio of 2 mg / ml, then added to a polytetrafluoroethylene inner liner and loaded into a reaction kettle, and reacted at 160 - 180 °C for 10 - 12 h in a forced-air drying oven. After the reaction is completed, the sample is collected by centrifugation and then dried at 60 - 80 °C for 8 - 10 h in a forced-air drying oven to obtain the porous rod-shaped carrier LaCeO 2 .

[0020] Further, step 3) is specifically as follows:

[0021] 3.1) Disperse the LaCeO 2 obtained in step 2) into a mixed solution of deionized water and methanol, and ultrasonically disperse it evenly; add the H 2 PtCl 6 solution containing Pt to the dispersed solution, and then irradiate it with a Xe lamp under stirring conditions for 3 - 4 h under Ar atmosphere protection; after the reaction is completed, the solid product is collected by centrifugation and placed in an electrothermal forced-air drying oven, and dried at 60 - 80 °C for 8 - 10 h to collect the product;

[0022] Among them, the ratio of LaCeO 2、 deionized water, methanol and the H 2 PtCl 6 solution containing Pt is 300 - 500∶36 - 60∶4 - 6.6∶0.3 (mg∶mL∶mL∶mL); H 2PtCl 6 The content of Pt in the solution is 5 mg / mL;

[0023] The power of the Xe lamp is 200 - 350 W;

[0024] 3.2) Place the product of step 3.1) in a 10 vol% H 2 / Ar atmosphere, heat it to 350 - 450 °C at a rate of 5 °C / min, and calcine for 2 hours to obtain the supported catalyst Pt cluster / LaCeO 2 .

[0025] Meanwhile, the present invention also provides a supported catalyst Pt cluster / LaCeO 2 prepared by the above preparation method, and its application as a catalyst in the aqueous-phase reforming of methanol to hydrogen. This catalyst can effectively solve the problems of the existing catalyst, such as complex preparation process and difficulty in balancing high selectivity and high activity in the steam reforming of methane reaction. It can avoid the generation of CO under high-temperature reaction conditions and further improve the hydrogen production efficiency of methane.

[0026] Furthermore, the loading amount of Pt is 0.5 wt%.

[0027] A method for low-temperature steam reforming of methane to hydrogen, characterized in that the operation is as follows:

[0028] Mix the catalyst Pt cluster / LaCeO 2 prepared by the above preparation method with quartz sand uniformly and place it in a fixed-bed reactor to introduce a stable mixed atmosphere (10 mL min -1 CH 4 , 15 mL min -1 N 2 and 40 mL min -1 H 2 O) for reaction, with WHSV of 39,000 mL g -1 h -1 , and the reaction temperature is 300 - 500 °C. After the reaction is completed, high-purity hydrogen is obtained. The specific operation is: mix the Pt cluster / LaCeO 2 catalyst with quartz sand and put it into a fixed-bed reaction tube (wherein, the volume ratio of the Pt cluster / LaCeO 2 catalyst to quartz sand is 1:3), and then introduce a mixed atmosphere of 65 ml min -1 (H 2 :N 2 :H 2The reaction is carried out under O = 2:8:3), with a WHSV of 39,000 mL g -1 h -1 , the reaction temperature is 300 - 500 °C, and the reaction pressure is set at 0.1 Mpa. During the reaction process, the tail gas of the fixed-bed reactor is connected to a gas chromatograph, and the gas components are analyzed online through the gas chromatograph TCD and FID, and the amounts of substances of H 2 , CO, CH 4 and CO 2 are calculated.

[0029] Principle of the present invention:

[0030] First, the present invention prepares a porous nanorod-shaped Pt cluster / LaCeO 2 catalyst with uniform morphology through a simple two-step hydrothermal method and photo-assisted deposition method, and then calcines it in an H 2 / Ar atmosphere. The overall design idea is to activate methane and water at different sites (the noble metal Pt and the carrier LaCeO 2 two activation sites) by designing double sites. In addition, combined with the ratio of methane and water in the reaction (methane∶water = 1∶4) and the relatively low reaction temperature, the high hydrogen production efficiency of methane is further ensured. The present invention controls the ratio of methane and water in the reaction of the methane steam reforming catalyst and the reaction temperature (300 - 500 °C). Finally, through performance testing, it is found that the catalyst Pt cluster / LaCeO 2 exhibits good catalytic activity in the methane steam reforming for hydrogen production reaction.

[0031] Advantages of the present invention:

[0032] 1. The present invention provides a preparation strategy for a catalyst that can simultaneously activate methane and water and effectively promote the production of CO 2 (not the by-product CO) in methane steam reforming for hydrogen production. Using porous nanorod-shaped LaCeO 2 as the carrier, cluster Pt is loaded by photo-assisted deposition (Pt forms a chemical bond with O on the carrier through Pt - O bonds), generating a catalyst Pt cluster / LaCeO 2 with a uniform size and porous nanorod-shaped structure. The whole preparation process is simple, requires less raw materials, has high economic benefits, and effectively solves the selectivity problem of low hydrogen production efficiency of methane in methane steam reforming for hydrogen production.

[0033] 2. The Pt cluster / LaCeO 2 catalyst prepared by the present invention has a high H 2 generation rate and CH4 Hydrogen production efficiency (> 3.90 mol H2 mol CH4 -1 ), that is, while accelerating the hydrogen production rate, it also avoids the generation of by-product CO, effectively solving the problem of low hydrogen production efficiency in the steam reforming of methane to hydrogen reaction and avoiding the additional steps of further purification of the subsequent gas. 4 Brief Description of the Drawings

[0034] Figure 1 Pt with different La contents cluster / LaCeO 2 Catalyst characterization diagrams and catalytic performances: a is the X-ray diffraction pattern; b is the partially enlarged X-ray diffraction pattern; c is the CH 4 conversion rate comparison diagram of different catalysts; d is the CH 4 hydrogen production efficiency comparison of different catalysts;

[0035] Figure 2 Comparison diagrams of catalysts with different Pt contents in Example 1 and Examples 3-6: a is the comparison diagram of CH 4 conversion rate of catalysts with different Pt loadings; b is the CO selectivity comparison diagram of catalysts with different Pt loadings;

[0036] Figure 3 LaCeO 2 Morphology and element distribution diagrams during the preparation process: a is the transmission electron microscope image; b is the high-resolution transmission electron microscope image; c is the high-angle annular dark field and the corresponding element distribution diagram;

[0037] Figure 4 Morphology characterization diagrams of different catalysts: a is Pt cluster / LaCeO 2 ; b is Pt cluster / CeO 2 ; c is Pt 1 / LaCeO 2 ; d is Pt NP / LaCeO 2 ;

[0038] Figure 5 High-angle annular dark field diagrams of catalysts with different Pt loadings in Examples 4-6: a is Example 4; b is Example 5; c is Example 6;

[0039] Figure 6 Oxygen vacancy characterization analysis of different catalysts: a is the La 3d analysis of different catalysts by XPS; b is the Ce 3d analysis of different catalysts by XPS; c is the O 1sAnalysis; d is the Raman spectrum analysis of different catalysts;

[0040] Figure 7 is the characterization analysis of synchrotron radiation of different catalysts: a is the XANES spectrum; b is the Fourier transform EXAFS spectrum; c is the comparison relationship between the Pt bond length and hydrogen production rate of different catalysts;

[0041] Figure 8 is Pt cluster / LaCeO 2 Catalytic performance diagram of the catalyst for hydrogen production by steam reforming of methane: a is the comparison diagram of CH 4 conversion rates of different catalysts; b is the CH 4 hydrogen production efficiency comparison; c is Pt cluster / LaCeO 2 Compare the H 2 production rate and CH 4 hydrogen production efficiency of different catalysts; d is Pt cluster / LaCeO 2 Stability test diagram of the catalyst. Specific implementation mode

[0042] The present invention discloses a preparation method of a catalyst for hydrogen production by steam reforming of methane. The technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments.

[0043] Example 1

[0044] Prepare the supported catalyst Pt cluster / LaCeO 2 , including the following steps:

[0045] (1) Prepare the La-Ce(OH) 3 / CeO 2 precursor

[0046] First, add 70 mL of ultrapure water to a 100 mL glass bottle and place a magnetic stirrer. Then, slowly add 19.2 g of sodium hydroxide to 70 mL of ultrapure water and stir for 30 minutes. After the NaOH solution cools, slowly dropwise add the prepared solution containing La 3+ (consisting of 4 mmol Ce(NO 3 ) 3 ·6H 2 O and 0.2 mmol La(NO 3 ) 3 ·6H 2O is added to 10 mL of ultrapure water and ultrasonicated for dispersion to prepare it. During the dropping process, the solution will gradually turn milky white. After the dropping is complete, stir at room temperature for 30 minutes, transfer it into a glass bottle, and react at 100 °C in a forced-air drying oven for 24 h. After the reaction is completed, wash it three times alternately with water and alcohol, and then dry it in a forced-air drying oven at 60 °C for 8 h to obtain La-Ce(OH) 3 / CeO 2 precursor.

[0047] (2) Preparation of LaCeO 2 support

[0048] Disperse the La-Ce(OH) 3 / CeO 2 precursor obtained in step (1) in ultrapure water at an addition ratio of 2 mg / ml by ultrasonic dispersion, add it to a 100 mL polytetrafluoroethylene inner liner, place it in a reaction kettle, and react at 180 °C in a forced-air drying oven for 12 h. After the reaction is completed, centrifuge to collect the sample, and then dry it in a forced-air drying oven at 60 °C for 8 h to obtain the porous rod-shaped support LaCeO 2 .

[0049] (3) Preparation of the supported catalyst Pt cluster / LaCeO 2

[0050] (3.1) Weigh 300 mg of the support LaCeO 2 obtained in step (2) and disperse it in a mixed solution of 36 mL of deionized water and 4 mL of methanol by ultrasonic dispersion until uniform. After the support is dispersed uniformly, add 0.3 mL of H 2 PtCl 6 solution (Pt content: 5 mg / ml), and then irradiate it with a Xe lamp (350 W) under the protection of an Ar atmosphere for 3 h under stirring conditions. After the reaction is completed, centrifuge to collect the solid product and place it in an electrothermal forced-air drying oven, and dry it at 60 °C for 10 h.

[0051] (3.2) In a 10 vol% H 2 / Ar atmosphere, heat it to 350 °C at a rate of 5 °C / min and calcine for 2 hours to obtain the supported catalyst Pt cluster / LaCeO 2 (Pt: 0.5 wt.%, La: 5 wt.%).

[0052] Example 2

[0053] The difference from Example 1 is that: in step 1), 0.28 mmol of La(NO 3 ) 3 ·6H 2 O is added to obtain the sample Ptcluster / LaCeO 2 (La: 7 wt.%)

[0054] Example 3

[0055] The difference from Example 1 is that in step 1), 0.08 mmol of La(NO 3 ) 3 ·6H 2 O is added to obtain the sample Pt cluster / LaCeO 2 (La: 2 wt.%).

[0056] Example 4

[0057] The difference from Example 1 is that in step 3), 0.05 mL of H 2 PtCl 6 solution (Pt content: 5 mg / ml) is added to obtain the sample Pt cluster / LaCeO 2 (Pt: 0.3 wt.%, La: 5 wt.%).

[0058] Example 5

[0059] The difference from Example 1 is that in step 3), 0.48 mL of H 2 PtCl 6 solution (Pt content: 5 mg / ml) is added to obtain the sample Pt cluster / LaCeO 2 (Pt: 0.8 wt.%, La: 5 wt.%).

[0060] Example 6

[0061] The difference from Example 1 is that in step 3), 0.72 mL of H 2 PtCl 6 solution (Pt content: 5 mg / ml) is added to obtain the sample Pt cluster / LaCeO 2 (Pt: 1.2 wt.%, La: 5 wt.%).

[0062] Comparative Example 1

[0063] The difference from Example 1 is that in step 1), La(NO 3 ) 3 ·6H 2 O is not added to obtain the sample Pt cluster / CeO 2 .

[0064] Comparative Example 2

[0065] The difference from Example 1 is that in step 3), 0.05 mL of H 2 PtCl 6 solution (Pt content: 5 mg / ml) was added to obtain the sample Pt 1 / LaCeO 2 (Pt: 0.2 wt.%, La: 5 wt.%).

[0066] Comparative Example 3

[0067] The difference from Example 1 is that in step 3), 1 mL of H 2 PtCl 6 solution (Pt content: 5 mg / ml) was added to obtain the sample Pt NP / LaCeO 2 (Pt: 1.5 wt.%, La: 5 wt.%).

[0068] To verify the effect, the following test examples were also carried out in the present invention:

[0069] I. Morphological and structural characterization of the catalyst Pt cluster / LaCeO 2 prepared in Example 1, and the catalysts obtained under different conditions in Examples 2-6 and Comparative Examples 1-3:

[0070] Figure 1 Comparison of catalysts with different La contents: As shown in a of Figure 1 , the doping of different amounts of La did not destroy the crystal phase of CeO 2 ; from b of Figure 1 , the shift of the CeO 2 lattice diffraction angle can be seen, which is caused by the doping of La; Figure 1 c and d of cluster / LaCeO 2 (La: 5 wt.%) show the performance of different La doping amounts on hydrogen production by steam reforming of methane. Pt 4 / LaCeO cluster (La: 5 wt.%) had a CH 2 conversion rate as high as 54.4% at 500 °C, approaching the equilibrium conversion rate (55.6%) at this time. It can be seen that the performance is the best when La is doped at 5%.

[0071] Figure 2 Figure 2 Comparison of catalysts with different Pt contents in Example 1 and Examples 3-6: As shown in a and b of (Pt: 0.5 wt.%) exhibited the best CH 4The conversion rate and the relatively low CO selectivity indicate that, overall, the performance is best when the Pt loading is 0.5%.

[0072] Figure 3 Using LaCeO as the carrier 2 Morphology and elemental distribution map of: As Figure 3 Shown in a of, LaCeO 2 Is a porous rod-like structure with uniform size; Figure 3 Shown in b of, the main exposed crystal plane is (110), and the interplanar spacing is 0.190 nm; Figure 3 Shown in c of, the Ce (green), O (blue), and La (yellow) elements are evenly distributed throughout the material.

[0073] Figure 4 High-angle annular dark-field images of different catalysts: Figure 4 As shown clearly in a of, Pt cluster / LaCeO 2 The presence of multiple clusters in the catalyst proves the successful loading of Pt clusters; Figure 4 Shown in b of, Pt cluster / CeO 2 Similar-sized Pt clusters appear in the catalyst; Figure 4 Shown in c of, Pt 1 / LaCeO 2 There are scattered bright spots on the surface of the catalyst, proving the successful loading of single-atom Pt; Figure 4 Shown in d of, its interplanar spacing is 0.225 nm, attributed to the (111) of Pt particles, indicating that large-sized Pt has been successfully loaded on the surface of the Pt NP / LaCeO 2 catalyst surface. It can be seen that when the Pt loading is less than or equal to 0.2 wt%, Pt exists in the form of single atoms, and when it is greater than or equal to 1.5 wt%, it will exist in the form of larger-sized particles.

[0074] Figure 5 High-angle annular dark-field images of catalysts with different Pt loadings in Examples 4 - 6: Similar-sized Pt clusters are shown in a, b, and c, indicating the successful loading of Pt clusters.

[0075] Figure 6 Characterization of oxygen vacancies: As Figure 6 Shown in a of, La is coordinated with O in the CeO 2 lattice, as Figure 6 Shown in b of, by fitting the Ce 3d orbital of each cerium oxide, it is found that the Pt cluster / LaCeO 2 catalyst has a Ce 3+ content of 35.2%, much higher than that of Ptcluster / CeO 2 ; As shown in Figure 6 c of cluster / LaCeO 2 catalyst, the highest Ce 3+ -O content is as high as 53.4%; compared with Pt cluster / LaCeO 2 and Pt cluster / CeO 2 catalysts' Raman spectra, the defect peak at 590 cm -1 of Pt cluster / LaCeO 2 catalyst is more obvious. Therefore, Pt cluster / LaCeO 2 has the highest oxygen defect concentration.

[0076] Figure 7 The synchrotron radiation spectra of different catalysts are as follows: As shown in Figure 7 a of cluster / LaCeO 2 catalyst, the chemical valence states of Pt 2 / LaCeO Figure 7 catalyst and other catalysts are all between Pt foil and PtO cluster / LaCeO 2 and Pt cluster / CeO 2 catalysts, the coordination form of Pt mainly coexists in the form of Pt-Pt and Pt-O. Pt 1 / LaCeO 2 catalyst is mainly Pt-O, and Pt NP / LaCeO 2 catalyst is mainly Pt-Pt. As shown in Figure 7 c of 4 cluster interface has rich electronic structure and is easier to realize the oxidation of CH 4 . Single atom is not conducive to the adsorption of CH 4 . Although the particle has strong adsorption of CH 2 , it is not conducive to the subsequent oxidation to form CO

[0077] From Figure 8 a of cluster / LaCeO 2 catalyst, compared with other catalysts, has a higher CH 4 conversion rate; Figure 8 b of 4 is the CHcluster / LaCeO 2 CH 4 The hydrogen production efficiency reaches 3.90 mol at 500 °C H2 mol CH4 -1 , which is consistent with the theoretical methane steam reforming reaction under experimental conditions. 4 Hydrogen production efficiency (3.91 mol H2 mol CH4 -1 ) is very close. Figure 8 The c shows Pt cluster / LaCeO 2 The catalyst H 2 Generation rate, Pt cluster / LaCeO 2 The catalyst H 2 The generation rate is very high, reaching 424.2 mol g Pt -1 h -1 , which is at least one order of magnitude higher than previously reported catalysts for hydrogen production from methane steam, and has a higher CH 4 Hydrogen production efficiency. Figure 8 Figure d is a stability test graph. Even at a high temperature of 500°C, Pt cluster / LaCeO 2 The catalyst also showed excellent stability towards RWGS. 4 The conversion rate remained almost unchanged and was close to the thermodynamic equilibrium yield, proving that Pt cluster / LaCeO 2 The catalyst has a stable structure and has the potential for commercialization.

[0078] In summary, the catalyst prepared by the present invention can solve the technical problems that the catalyst is easily deactivated at high temperature during the current methane steam reforming hydrogen production, it is difficult to achieve both high activity and high hydrogen selectivity, and the methane hydrogen production efficiency is low.

[0079] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should be included in the protection scope of the present invention.

Claims

1. A supported catalyst Pt cluster / A method for preparing LaCeO2, characterized in that: The following steps are involved: 1) In a cooled strong alkaline solution, a solution prepared by Ce salt, La salt and ultrapure water is added dropwise to prepare a LaCe(OH)3 / CeO2 precursor by a low-pressure hydrothermal method; 2) ultrasonically dispersing the LaCe(OH)3 / CeO2 precursor obtained in step 1) in ultrapure water, and then obtaining a porous rod-shaped carrier LaCeO2 by a high-pressure hydrothermal method; 3) Platinum is loaded on the carrier LaCeO2 obtained in step 2) by light-assisted deposition, and reduced in an atmosphere of argon and hydrogen to obtain a loaded catalyst Pt cluster / LaCeO2, wherein the loading amount of Pt is greater than 0.2wt% and less than 1.5wt%.

2. according to claim 1 described supported catalyst Pt cluster / A method for preparing LaCeO2, characterized in that: Step 1) is specifically as follows: Slowly add a strong base into a glass bottle filled with ultrapure water, stir and wait for the strong base solution to cool down, then slowly drop a solution prepared by Ce(NO3)3·6H2O, La(NO3)3·6H2O and ultrapure water. After the addition is complete, stir at room temperature and place in a glass bottle to react at 100-120°C for 12-24h. After the reaction is completed, wash alternately with water and alcohol several times, and then dry at 60-80°C for 8-12h to obtain La-Ce(OH)3 / CeO2 precursor.

3. according to claim 2 described supported catalyst Pt cluster / A method for preparing LaCeO2, characterized in that: In step 1), the strong base is NaOH or KOH; OH - The molar concentration in the reaction solution is 2-6 mol / L; The molar ratio of La to Ce is 1:10-50, and the molar concentration of Ce in the reaction solution is 40-60 mmol / L.

4. According to any one of claims 1 to 3, the supported catalyst Pt cluster / A method for preparing LaCeO2, characterized in that: In step 2), the La-Ce(OH)3 / CeO2 precursor is ultrasonically dispersed in ultrapure water at a ratio of 2 mg / ml, then added to a polytetrafluoroethylene liner and loaded into a reactor, and reacted in a forced air drying oven at 160-180°C for 10-12 hours. After the reaction is completed, the sample is collected by centrifugation and then placed in a forced air drying oven at 60-80°C for 8-10 hours to obtain a porous rod-shaped carrier LaCeO2.

5. according to claim 4 described supported catalyst Pt cluster / A method for preparing LaCeO2, characterized in that: Step 3) is specifically: 3.1) Disperse the LaCeO2 obtained in step 2) into a mixed solution of deionized water and methanol, and disperse it evenly by ultrasonication; add a H2PtCl6 solution containing Pt to the dispersed solution, and then irradiate it with a Xe lamp under stirring conditions for 3-4 hours under the protection of an Ar atmosphere; after the reaction is completed, collect the solid product by centrifugation and place it in an electric blast drying oven, dry it at 60-80°C for 8-10 hours, and collect the product; The ratio of LaCeO2, deionized water, methanol and H2PtCl6 solution containing Pt is 300-500: 36-60: 4-6.6: 0.3 (mg: mL: mL: mL); the content of Pt in the H2PtCl6 solution is 5 mg / mL; The power of Xe lamp is 200~350W; 3.2) The product of step 3.1) was placed in a 10 vol% H2 / Ar atmosphere, heated to 350-450°C at a rate of 5°C / min, and calcined for 2-4 hours to obtain a supported catalyst Pt cluster / LaCeO2.

6. A supported catalyst Pt cluster / LaCeO2, characterized by: The product is prepared by the preparation method described in any one of claims 1 to 5.

7. according to claim 6 described supported catalyst Pt cluster / LaCeO2, characterized by: The loading amount of Pt was 0.5 wt.%.

8. Pt prepared by any one of the preparation methods of claims 1 to 5 cluster / Application of LaCeO2 as catalyst in aqueous phase reforming of methanol to produce hydrogen.

9. A method for producing hydrogen by low-temperature methane steam reforming, characterized in that: The operation is as follows: The catalyst Pt prepared by any one of the preparation methods of claims 1 to 5 cluster / LaCeO2 and quartz sand are uniformly mixed and placed in a fixed bed reactor and a stable mixed atmosphere is introduced to react at a reaction temperature of 300-500°C. After the reaction is completed, hydrogen is obtained; The mixed atmosphere was 10 mL min -1 CH4, 15mL min -1 N2 and 40 mL min -1 H2O composition.

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