Vanadium-modified dehydrogenation catalyst and method for preparing the same

Abstract

The application belongs to the technical field of catalytic dehydrogenation, and particularly relates to a vanadium-modified dehydrogenation catalyst and a preparation method thereof. The catalyst is composed of M@V-KIT-6, wherein M is a main catalyst, V is an active component regulator, and KIT6 is a carrier. The application provides a catalyst for effectively improving the catalytic efficiency of an active metal and a preparation method thereof. A step-by-step impregnation doping-loading method is used to realize vanadium doping modification of the active metal, so as to effectively control the refinement of the active metal nanocrystalline grains and the improvement of the catalytic dehydrogenation performance. The application not only has a simple and easy-to-operate preparation method, but also has uniformly distributed nanometer palladium particles. The application effectively solves the problems of the current commercial noble metal catalyst, such as low catalytic activity, low selectivity and poor stability, and is suitable for the dehydrogenation application of hydrogen storage materials containing C-H bonds.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalytic dehydrogenation, and particularly relates to a vanadium-modified dehydrogenation catalyst and a preparation method thereof. BACKGROUND

[0002] Hydrogen energy has become a key component in the global future low-carbon strategy and green energy due to its high energy density, high heat value, wide source, and green and pollution-free characteristics. First, the utilization of hydrogen energy mainly includes four parts: hydrogen production, storage, transportation, and hydrogen use. Among them, safe and efficient hydrogen storage and transportation is the key to realizing the large-scale application of hydrogen energy and is also the bottleneck restricting the development of hydrogen energy. Therefore, a variety of hydrogen storage technologies have been developed worldwide, including hydrogen deep cooling liquefied hydrogen storage, ammonia liquefied hydrogen storage, solid hydride hydrogen storage, high-pressure gas cylinder tank hydrogen storage, organic liquid hydrogen storage, and porous material adsorption hydrogen storage.

[0003] Among them, the organic liquid hydrogen storage material is liquid at room temperature, which can realize safe storage and transportation of hydrogen gas at room temperature and normal pressure, making it one of the most promising hydrogen storage technologies. Its outstanding advantages lie in high hydrogen storage density, non-flammability, non-explosiveness, safety and reliability, and compatibility with existing oil transportation infrastructure. However, the organic liquid hydrogen storage material needs to be catalytically dehydrogenated at a certain temperature using a catalyst to release hydrogen, which involves the use of noble metal catalysts. However, due to the scarcity and non-renewability of noble metals such as Pt, Pd, and Rh, the cost is high, which cannot meet the demand of large-scale application. In addition, due to the high activity of noble metal catalysts, on the one hand, side reactions often occur during catalysis, resulting in reduced catalytic selectivity and shortening the cycle life of hydrogen storage materials; on the other hand, it also causes catalyst particle agglomeration and frequent poisoning, resulting in deactivation. These problems need to be solved, which restricts the further promotion of organic liquid hydrogen storage technology and the large-scale application of hydrogen energy technology.

[0004] Therefore, it is necessary to provide a new type of catalyst with high catalytic activity and high selectivity, while maintaining the stable existence of active components and a preparation method thereof. Ultimately, it is conducive to promoting the realization of large-scale development of hydrogen energy application. SUMMARY

[0005] The purpose of the present application is to overcome the above-mentioned problems in the prior art, provide a dehydrogenation catalyst with improved catalytic activity, selectivity and stability by effectively controlling the grain size and electronic structure of noble metal, and a preparation method thereof, and introduce V element into KIT6 as a substrate which can realize high specific surface area preparation and easy surface modification and doping to effectively control the grain size and electronic structure of the active component to greatly improve the catalytic performance.

[0006] In order to achieve the above technical purposes and achieve the above technical effects, the present application is realized by the following technical solutions:

[0007] The present application provides a vanadium modified dehydrogenation catalyst, which is composed of M@V-KIT-6, wherein,

[0008] M is a main catalyst, including any one or a combination of Pt, Pd, Ru, Rh, Ir, Co, Ni, Cu, Fe, wherein M must contain at least one noble metal; the molar percentage content of the main catalyst is 0.1% to 15%;

[0009] V is an active component regulator, and the molar percentage content is 0.001% to 5.0%;

[0010] The remaining content is the carrier KIT6.

[0011] Further, the active component regulator V is uniformly distributed on the surface and pores of KIT6, and is anchored between the carrier by oxygen atoms.

[0012] Further, the active component regulator V can effectively refine the nanocrystalline grain size of the active metal M and control its electronic structure.

[0013] Further, the nanocrystalline grain size of the active metal M is controlled to 1nm to 5nm.

[0014] The present application also provides a preparation method of a vanadium modified dehydrogenation catalyst, comprising the following steps:

[0015] 1) A certain amount of V precursor is dissolved in H2O2 solution, and is fully stirred and dissolved at room temperature to obtain a V precursor solution;

[0016] 2) A certain amount of KIT6 is added to the V precursor solution and stirred uniformly, and after standing for a certain time, it is dried overnight at a certain temperature to remove water, and finally calcined at a certain temperature to obtain V-KIT6 with a surface modified by vanadium;

[0017] 3) A certain amount of M precursor solution is added to V-KIT6, heated and stirred until no visible water, further dried at 80℃ overnight to obtain M@V-KIT6 precursor powder;

[0018] 4) The M@V-KIT6 precursor powder is calcined and reduced to obtain the M@V-KIT6 dehydrogenation catalyst.

[0019] Further, in step 1), the V precursor includes any one or a combination of ammonium metavanadate, sodium metavanadate, vanadium pentoxide and vanadium dioxide.

[0020] Further, in step 2), the atomic ratio of V / Si is 0.001-1; the standing time is 3-24h; the drying temperature is 60-120℃; and the calcination temperature is 300-600℃.

[0021] Further, in step 3), the M precursor comprises any one or a combination of nitrate, halide and acetate of the M metal; and the atomic ratio of V / M is 0.01-5.

[0022] Further, in step 4), the calcination temperature is 300-600℃; the calcination heating rate is 0.5-20℃ / min; the calcination time is 1-6h; the reduction mode is reduction in a hydrogen atmosphere, and the reduction temperature is 300-600℃; the reduction heating rate is 1-10℃ / min; and the reduction time is 0.5-6h.

[0023] The application also provides an application of the vanadium-modified dehydrogenation catalyst in catalyzing C-H bond activation and dehydrogenation reaction.

[0024] The application has the following advantages:

[0025] 1. The application uses non-noble metal V as an activity regulator of a noble metal main catalyst, which can refine the grain size of the active metal, so that more active sites can be obtained, and the catalyst activity is improved; and the electronic structure of the noble metal main catalyst is regulated, so that the catalyst selectivity and stability are improved, and the catalytic performance of the catalyst is far superior to that of the traditional noble metal catalyst, and low-temperature controllable rapid dehydrogenation of the hydrogen storage material containing C-H bond can be realized.

[0026] 2. All raw materials of the catalyst are widely available, low in cost, simple in process, short in cycle, and high in yield, which can greatly improve the catalytic performance and stability of the dehydrogenation catalyst, effectively prolong the service life of the catalyst, thereby reducing the dehydrogenation reaction cost, and realizing the large-scale application of the catalyst in the catalytic dehydrogenation of the hydrogen storage material.

[0027] Of course, it is not necessary for any product implementing the application to achieve all the advantages above. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the application will be described below in a clear and complete manner. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0029] This invention first employs a stepwise impregnation-doping-loading method to achieve vanadium doping modification of active metals, effectively refining the active metal nanocrystals and regulating their electronic structure, thereby improving the catalyst's catalytic dehydrogenation activity, selectivity, and stability. This invention not only features a simple and easy-to-operate preparation method with reasonable cost and stable process, but also produces uniformly and stably distributed palladium nanoparticles. It effectively solves the problems of insufficient catalytic activity, selectivity, and poor stability found in current commercial precious metal catalysts, making it suitable for dehydrogenation applications in hydrogen storage materials containing C-H bonds, thus enabling the large-scale application of hydrogen energy.

[0030] Specific embodiments of the present invention are as follows:

[0031] Example 1

[0032] 0.5 g of ammonium metavanadate was dissolved in H₂O₂ solution and stirred thoroughly at room temperature to obtain a V precursor solution. 1 g of KIT₆ with a high specific surface area was weighed, and a certain amount of the V precursor solution was added to KIT₆ at an atomic ratio of V:Si = 1:50. The mixture was stirred until homogeneous, allowed to stand for 12 h, and then dried overnight at 100 °C to remove water. Subsequently, it was calcined at 400 °C to obtain V-KIT₆ with a vanadium-coated surface. 0.5 g of platinum chloride was weighed to prepare a 0.1 mol / L Pt precursor solution, and a certain amount of the Pt precursor solution was added at an atomic ratio of V / Pt = 1:1. Add to V-KIT6, heat and stir until no visible water is visible, then dry overnight at 80℃ to obtain Pt@V-KIT6 precursor powder; calcine the Pt@V-KIT6 precursor powder at 10℃ / min to 500℃ for 3h, then cool to room temperature in the furnace, and finally reduce it at 10℃ / min to 500℃ for 3h under a hydrogen atmosphere; finally, a Pt@V-KIT6 dehydrogenation catalyst with a grain size of 3.1nm is obtained.

[0033] With an active metal to hydrogen storage material ratio of 1:200, the reaction was carried out in a dehydrogenation reactor at the temperature set in the table for 6 hours. The results are shown in Table 1.

[0034] Table 1

[0035]

[0036] Example 2

[0037] Take 0.5 grams of sodium metavanadate and dissolve it in H2O2 solution, fully stir and dissolve at room temperature to obtain a precursor solution of V. Take 1 gram of KIT6 with high specific surface area, add a certain amount of precursor solution of V to KIT6 according to the atomic ratio V:Si = 1:20, stir uniformly, stand for 8 hours, then dry at 80°C overnight to remove water, and then calcine at 450°C to obtain V-KIT6 with vanadium covered on the surface; take 0.5 grams of palladium nitrate and prepare a 0.1 mol / L Pd precursor solution, add a certain amount of Pd precursor solution to V-KIT6 according to the atomic ratio V:Pd = 2:1, heat and stir until no visible water, then dry overnight at 80°C to obtain Pd@V-KIT6 precursor powder; first heat the Pd@V-KIT6 precursor powder to 400°C at a rate of 10°C / min, calcine for 3 hours, then cool to room temperature in the furnace, and finally heat to 400°C at a rate of 10°C / min under a hydrogen atmosphere and reduce for 3 hours; finally, a Pd@V-KIT6 dehydrogenation catalyst with a grain size of 2.8 nm is obtained.

[0038] According to active metal:hydrogen storage material = 1:200, react in a high-temperature high-pressure reaction kettle in a dehydrogenation reactor for 6 hours at the temperature set in the table to obtain the results shown in Table 2:

[0039] Table 2

[0040]

[0041] Example 3

[0042] Take 0.5 grams of vanadium dioxide and dissolve it in H2O2 solution, fully stir and dissolve at room temperature to obtain a precursor solution of V. Take 1 gram of KIT6 with high specific surface area, add a certain amount of precursor solution of V to KIT6 according to the atomic ratio V:Si = 1:100, stir uniformly, stand for 12 hours, then dry at 1000°C overnight to remove water, and then calcine at 500°C to obtain V-KIT6 with vanadium covered on the surface; take 0.2 grams of palladium nitrate and 0.2 grams of platinum chloride and prepare 0.1 mol / L precursor solutions of Pd and Pt, add a certain amount of precursor solutions of Pd and Pt to V-KIT6 according to the atomic ratio V:Pd:Pt = 0.5:1:1, heat and stir until no visible water, then dry overnight at 100°C to obtain PdPt@V-KIT6 precursor powder; first heat the PdPt@V-KIT6 precursor powder to 500°C at a rate of 10°C / min, calcine for 3 hours, then cool to room temperature in the furnace, and finally heat to 400°C at a rate of 5°C / min under a hydrogen atmosphere and reduce for 3 hours; finally, a PdPt@V-KIT6 dehydrogenation catalyst with a grain size of 2.6 nm is obtained.

[0043] The active metal: hydrogen storage material = 1:200, in a high temperature and high pressure reactor, in the dehydrogenation reactor, the temperature in the table is set to react for 6h, and the results are shown in Table 3:

[0044] Table 3

[0045]

[0046] Comparative Example 1

[0047] 1 gram of KIT6 with high specific surface area was weighed into a beaker, 0.2 grams of palladium nitrate and 0.2 grams of platinum chloride were weighed and respectively prepared into 0.1 mol / L Pd and Pt precursor solution, a certain amount of Pd and Pt precursor solution was added to KIT6 according to the atomic ratio of Pd:Pt 1:1, heated and stirred until no visible water, then dried overnight at 100℃, to obtain PdPt@KIT6 precursor powder; the PdPt@KIT6 precursor powder was first calcined at 500℃ at a temperature rising rate of 10℃ / min for 3h, then the furnace was cooled to room temperature, and finally reduced at 400℃ under hydrogen atmosphere at a temperature rising rate of 5℃ / min for 3h; finally, the PdPt@KIT6 dehydrogenation catalyst with a grain size of 5.8nm was obtained.

[0048] In addition, a group of commercial noble metal Pd / Al2O3 dehydrogenation test results under the same conditions are also added.

[0049] The active metal: hydrogen storage material = 1:200, in a high temperature and high pressure reactor, in the dehydrogenation reactor, the temperature in the table is set to react for 6h, and the results are shown in Table 4:

[0050] Table 4

[0051]

[0052] From the results of the above three groups of examples and comparative examples, it can be seen that the presence of V effectively refines the grain size of the active metal, greatly improves the catalytic performance of the dehydrogenation catalyst. Therefore, the present application can obtain an effective vanadium modified active metal dehydrogenation catalyst and its preparation method.

[0053] The preferred embodiments of the present application disclosed above are only used to help explain the present application. The preferred embodiments do not describe all the details, nor limit the application to the specific embodiments. Obviously, many modifications and changes can be made according to the content of the present application. The embodiments are selected and described in detail in order to better explain the principles and practical applications of the present application, so that those skilled in the art can well understand and utilize the present application. The present application is limited by the claims and their full scope and equivalents.

Claims

1. A vanadium-modified dehydrogenation catalyst, characterized in that, The vanadium-modified dehydrogenation catalyst has the composition M@V-KIT6, wherein, M is the main catalyst, comprising any one or more combinations of Pt, Pd, Ru, Rh, Ir, Co, Ni, Cu, and Fe, wherein M must contain at least one noble metal; the molar percentage content of the main catalyst is 0.1% to 15%. V is an active ingredient regulator, with a molar percentage content of 0.001% to 5.0%; The remaining content is carrier KIT6; The preparation method of the vanadium-modified dehydrogenation catalyst includes the following steps: 1) Weigh a certain amount of V precursor and dissolve it in H2O2 solution. Stir thoroughly at room temperature to dissolve and obtain V precursor solution; 2) Weigh a certain amount of KIT6 and add it to the precursor solution of V, mix and stir evenly. After standing for a certain time, dry it overnight at a certain temperature to remove water, and finally calcine it at a certain temperature to obtain V-KIT6 with vanadium surface modification. 3) Weigh a certain amount of M precursor solution and add it to V-KIT6. Heat and stir until no visible water is visible. Then dry at 80°C overnight to obtain M@V-KIT6 precursor powder. 4) The M@V-KIT6 precursor powder was calcined and then reduced to obtain the M@V-KIT6 dehydrogenation catalyst.

2. The vanadium-modified dehydrogenation catalyst according to claim 1, characterized in that, The active component regulator V is uniformly distributed on the surface and in the pores of KIT6, and is anchored to the carrier by oxygen atoms.

3. The vanadium-modified dehydrogenation catalyst according to claim 1, characterized in that, The active component regulator V can effectively refine the size of active metal M nanocrystals and regulate their electronic structure.

4. The vanadium-modified dehydrogenation catalyst according to claim 1, characterized in that, The nanocrystal size of the active metal M is controlled between 1 nm and 5 nm.

5. The vanadium-modified dehydrogenation catalyst according to claim 1, characterized in that, In step 1), the V precursor includes any one or more combinations of ammonium metavanadate, sodium metavanadate, vanadium pentoxide, and vanadium dioxide.

6. The vanadium-modified dehydrogenation catalyst according to claim 1, characterized in that, In step 2), the V / Si atomic ratio is 0.001 to 1; the standing time is 3 to 24 hours; the drying temperature is 60 to 120°C; and the calcination temperature is 300°C to 600°C.

7. The vanadium-modified dehydrogenation catalyst according to claim 1, characterized in that, In step 3), the M precursor includes any one or more combinations of nitrates, halides and acetates of the M metal; the V / M atomic ratio is 0.01 to 5.

8. The vanadium-modified dehydrogenation catalyst according to claim 1, characterized in that, In step 4), the calcination temperature is 300℃~600℃; the calcination heating rate is 0.5℃ / min~20℃ / min; the calcination time is 1h~6h; the reduction method is reduction in a hydrogen atmosphere, the reduction temperature is 300℃~600℃; the reduction heating rate is 1℃ / min~10℃ / min; and the reduction time is 0.5h~6h.

9. The application of the vanadium-modified dehydrogenation catalyst according to any one of claims 1 to 4 in the catalytic C-H bond activation dehydrogenation reaction.

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