Ni-based non-noble metal catalyst, preparation method and application in catalytic dehydrogenation of organic liquid

Abstract

The present application relates to a kind of Ni-based non-noble metal catalyst, preparation method and application in organic liquid catalytic dehydrogenation, belong to the technical field of catalyst preparation.The active component of the catalyst is Ni nanoparticle, carrier is γ-alumina, wherein the loading of Ni nanoparticle is 9.0%-20.0%, the particle size of Ni nanoparticle is 3-8nm, the particle size of γ-alumina is 20-50nm.The catalyst of the present application can enhance the dispersion of Ni based on the interaction between γ-alumina carrier and metal, form smaller size Ni nanoparticles, so that the catalyst has better activity and stability.The catalyst of the present application can realize the dehydrogenation conversion rate of more than 86% of full hydrogenation N-ethylcarbazole within 50min under relatively mild reaction conditions.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation technology, specifically relating to a Ni-based non-precious metal catalyst, its preparation method, and its application in the catalytic dehydrogenation of organic liquids. Background Technology

[0002] Hydrogen energy is one of the future energy sources, but hydrogen storage and transportation have always been a bottleneck in its development. Liquid organic hydrogen carriers are considered one of the ultimate solutions to the hydrogen storage and transportation problem due to their high hydrogen storage capacity, high safety, ease of thermal management, and compatibility with existing equipment. Currently, several representative liquid organic hydrogen carriers, such as toluene, dibenzyltoluene, carbazole, and indole, have been extensively studied.

[0003] Compared to benzene-based supports, nitrogen-doped heterocyclic compounds exhibit lower dehydrogenation temperatures. For example, N-ethylcarbazole can achieve complete dehydrogenation below 200°C, with a theoretical hydrogen storage density of up to 5.79%, providing favorable conditions for its practical application. For N-ethylcarbazole, commonly used hydrogen absorption and desorption catalysts are mostly Ru-based or Pd-based catalysts supported on alumina. These noble metal catalysts exhibit good activity but are costly. The performance of reported non-noble metal catalysts is not yet sufficient to meet the practical application requirements of N-ethylcarbazole, and further breakthroughs are needed.

[0004] Therefore, how to further improve the hydrogen absorption and dehydrogenation activity of non-precious metal catalysts for N-ethylcarbazole is a key issue of concern to researchers in this field. Summary of the Invention

[0005] The purpose of this invention is to address the problems in the prior art by providing a Ni-based non-noble metal catalyst, its preparation method, and its application in the catalytic dehydrogenation of organic liquids. This invention improves the catalyst activity by controlling the particle size of Ni nanoparticles under specific preparation conditions. The synthesized catalyst, under relatively mild reaction conditions, can achieve a dehydrogenation conversion of over 86% for N-ethylcarbazole within 50 minutes and exhibits good cycle stability.

[0006] The technical problem to be solved by the present invention is solved by the following technical solution: This invention discloses a Ni-based non-precious metal catalyst, wherein the active component of the catalyst is Ni nanoparticles and the support is γ-alumina, wherein the loading of Ni nanoparticles is 9.0-20.0%, the particle size of Ni nanoparticles is 3-8 nm, and the particle size of γ-alumina is 20-50 nm.

[0007] Preferably, the Ni-based non-noble metal catalyst of the present invention is prepared by the following steps: 1) Weigh γ-alumina powder and add it to deionized water. Disperse it evenly under stirring to obtain γ-alumina dispersion. 2) Weigh out the nickel salt precursor and dissolve it in deionized water to prepare a nickel salt solution; 3) Slowly add the nickel salt solution obtained in step 2) to the γ-alumina dispersion obtained in step 1), and then heat and stir to fully impregnate the γ-alumina carrier to obtain a mixed solution; 4) Transfer the mixture obtained in step 3) to a rotary evaporator for evaporation and dryness, and grind the product to obtain catalyst precursor powder; 5) The catalyst precursor powder obtained in step 4) is reduced at high temperature in a hydrogen atmosphere, and then the product is collected by natural cooling in a hydrogen atmosphere to obtain the Ni-based non-precious metal catalyst.

[0008] Preferably, the nickel salt precursor in step 2) of the present invention is one of nickel nitrate hydrate or nickel acetate hydrate, or a mixture of both.

[0009] Preferably, in step 3), the heating and stirring are carried out at a temperature of 40–80°C and the soaking time is 1–5 h; in step 4), the water bath temperature for rotary evaporation is 50–80°C; and in step 5), the high-temperature reduction is carried out at a temperature of 400–480°C, the reduction time is 2–4 h, and the heating rate is 3–10°C / min.

[0010] This invention relates to the application of a Ni-based non-precious metal catalyst for the dehydrogenation of N-ethylcarbazole, which is a fully hydrogenated liquid organic hydrogen support.

[0011] More preferably, the catalyst is mixed with liquid organic hydrogen support fully hydrogenated N-ethylcarbazole at a mass ratio of 1:10, the reaction pressure is atmospheric pressure, the reaction temperature is 220°C, and the rotation speed is 100-900 rpm.

[0012] Compared with existing technologies, the technical advantages of the Ni-based non-noble metal catalyst, its preparation method, and its application in this invention are as follows: 1) The catalyst of the present invention is based on the interaction between the γ-alumina support and metallic Ni, which can enhance the dispersion of Ni nanoparticles and form smaller Ni nanoparticles, so that the catalyst has both good activity and stability.

[0013] 2) The catalyst preparation process of the present invention is simple, low in cost, and easy to scale up.

[0014] 3) The catalyst of the present invention can achieve a total hydrogenation-N-ethylcarbazole dehydrogenation conversion rate of over 86% within 50 minutes under relatively mild reaction conditions. Attached Figure Description

[0015] Figure 1 This is a TEM image of the Ni-based non-noble metal catalyst prepared in Example 1 of this invention.

[0016] Figure 2 This is a particle size distribution diagram of Ni nanoparticles in the Ni-based non-noble metal catalyst prepared in Example 1 of this invention.

[0017] Figure 3 This is a comparison of hydrogen desorption curves of Ni-based non-noble metal catalysts prepared in different embodiments of the present invention.

[0018] Figure 4 This is a comparison of the hydrogen desorption curves of the Ni-based non-noble metal catalysts prepared in Example 1 and Comparative Example 1 of this invention.

[0019] Figure 5 This is a comparison of the hydrogen desorption curves of the Ni-based non-noble metal catalysts prepared in Example 1 and Comparative Example 2 of this invention.

[0020] Figure 6 This is a comparison of the hydrogen desorption curves of the Ni-based non-noble metal catalysts prepared in Example 1 and Comparative Example 3 of this invention.

[0021] Figure 7 This is a comparison of the hydrogen desorption curves of the Ni-based non-noble metal catalysts prepared in Example 1 and Comparative Example 4 of this invention.

[0022] Figure 8 This is a TEM image of the Ni-based non-noble metal catalyst prepared in Comparative Example 4 of this invention.

[0023] Figure 9 This is a bar chart comparing the hydrogen release of the Ni-based non-precious metal catalyst prepared in Example 1 of this invention after multiple reuses.

[0024] Figure 10 This is a TEM image of the Ni-based non-noble metal catalyst prepared in Example 1 of this invention after multiple reuses.

[0025] Figure 11 This is a particle size distribution diagram of Ni nanoparticles after repeated use of the Ni-based non-noble metal catalyst prepared in Example 1 of this invention. Detailed Implementation

[0026] The technical content and implementation methods of the present invention will be further described in detail below with reference to embodiments, comparative examples and accompanying drawings.

[0027] Example 1: This embodiment provides a method for preparing a Ni-based non-noble metal catalyst, including the following steps: (1) Weigh 3 g of γ-alumina powder with a particle size of 20 nm into 50 mL of deionized water and disperse it evenly under stirring to obtain γ-alumina dispersion. (2) Weigh 2.5 g of nickel nitrate hexahydrate and dissolve it completely in 50 mL of deionized water to prepare a nickel nitrate solution; (3) The nickel nitrate solution obtained in step (2) is slowly added to the γ-alumina dispersion obtained in step (1), and then heated and stirred for 2 h to fully impregnate the γ-alumina carrier and obtain a mixed solution. The heating temperature is 50℃. (4) The mixture obtained in step (3) is transferred to a rotary evaporator and evaporated to dryness in a water bath at 60°C. The product is then ground to obtain catalyst precursor powder. (5) The catalyst precursor powder obtained in step (4) is reduced at 450°C for 3 h in a hydrogen atmosphere with a heating rate of 3°C / min, and then the product is collected by natural cooling in a hydrogen atmosphere.

[0028] Example 2: This embodiment provides a method for preparing a Ni-based non-noble metal catalyst, including the following steps: (1) Weigh 3 g of γ-alumina powder with a particle size of 20 nm into 50 mL of deionized water and disperse it evenly under stirring to obtain γ-alumina dispersion. (2) Weigh 2.5 g of nickel acetate tetrahydrate and dissolve it completely in 50 mL of deionized water to prepare a nickel acetate solution; (3) The nickel acetate solution obtained in step (2) is slowly added to the γ-alumina dispersion obtained in step (1), and then heated and stirred for 3 h to fully impregnate the γ-alumina carrier and obtain a mixed solution. The heating temperature is 50℃. (4) The mixture obtained in step (3) is transferred to a rotary evaporator and evaporated to dryness in a water bath at 60°C. The product is then ground to obtain catalyst precursor powder. (5) The catalyst precursor powder obtained in step (4) is reduced at 400°C for 3 h in a hydrogen atmosphere with a heating rate of 3°C / min, and then the product is collected by natural cooling in a hydrogen atmosphere.

[0029] Example 3: This embodiment provides a method for preparing a Ni-based non-noble metal catalyst, including the following steps: (1) Weigh 3 g of γ-alumina powder with a particle size of 50 nm into 50 mL of deionized water and disperse it evenly under stirring to obtain γ-alumina dispersion. (2) Weigh 1.5 g of nickel nitrate hexahydrate and dissolve it completely in 40 mL of deionized water to prepare a nickel nitrate solution; (3) The nickel nitrate solution obtained in step (2) is slowly added to the γ-alumina dispersion obtained in step (1), and then heated and stirred for 2 h to fully impregnate the γ-alumina carrier and obtain a mixed solution. The heating temperature is 70℃. (4) The mixture obtained in step (3) is transferred to a rotary evaporator and evaporated to dryness in a water bath at 70°C. The product is then ground to obtain catalyst precursor powder. (5) The catalyst precursor powder obtained in step (4) is reduced at 480°C for 2 h in a hydrogen atmosphere with a heating rate of 10°C / min, and then the product is collected by natural cooling in a hydrogen atmosphere.

[0030] Example 4: This embodiment provides a method for preparing a Ni-based non-noble metal catalyst, including the following steps: (1) Weigh 3 g of γ-alumina powder with a particle size of 30 nm into 50 mL of deionized water and disperse it evenly under stirring to obtain γ-alumina dispersion. (2) Weigh 3.6 g of nickel nitrate hexahydrate and dissolve it completely in 70 mL of deionized water to prepare a nickel nitrate solution; (3) The nickel nitrate solution obtained in step (2) is slowly added to the γ-alumina dispersion obtained in step (1), and then heated and stirred for 2 h to fully impregnate the γ-alumina carrier and obtain a mixed solution. The heating temperature is 70℃. (4) The mixture obtained in step (3) is transferred to a rotary evaporator and evaporated at 70°C in a water bath. The product is then ground to obtain catalyst precursor powder. (5) The catalyst precursor powder obtained in step (4) is reduced at 450°C for 2 h in a hydrogen atmosphere with a heating rate of 5°C / min, and then the product is collected by natural cooling in a hydrogen atmosphere.

[0031] Comparative Example 1: The catalyst preparation method in this comparative example is completely the same as that in Example 1, except that the 3 g of γ-alumina powder with a particle size of 20 nm in step (1) is replaced with 3 g of nano-silica powder with a particle size of 20 nm, i.e. the catalyst support is different.

[0032] Comparative Example 2: The preparation method of the catalyst in this comparative example is exactly the same as that in Example 1, except that the particle size of the γ-alumina powder in step (1) is changed from 20 nm to 300 nm.

[0033] Comparative Example 3: The preparation method of the catalyst in this comparative example is the same as that in Example 1, except that the weight of nickel nitrate hexahydrate in step (2) is changed from 2.5 g to 4.0 g, that is, the loading of the active component of the catalyst is different.

[0034] Comparative Example 4: The preparation method of the catalyst in this comparative example is completely the same as that in Example 1, except that the rotary drying in step (4) is changed to drying in a vacuum drying oven at 60°C, that is, the impregnation and drying conditions of the catalyst are different.

[0035] The catalysts prepared in Examples 1-4 and Comparative Examples 1-4 were subjected to catalytic dehydrogenation tests on N-ethylcarbazole supported on liquid organic hydrogen carriers: Weigh 1 g of the corresponding catalyst and 10 g of fully hydrogenated N-ethylcarbazole and mix them in a round-bottom flask. Add the mixture to the rotor, and connect the flask opening to a hydrogen mass flow meter via a pipeline. Preheat the heat transfer oil in the oil bath to 220°C, then place the round-bottom flask containing the reactants into the oil bath. Start timing simultaneously. The catalyst begins to catalyze the dehydrogenation of the liquid organic hydrogen support under heating and stirring conditions. The rotor speed is 300 rpm, and the change in hydrogen production volume over time is recorded.

[0036] TEM images of the catalyst prepared in Example 1 of this invention and particle size distribution diagrams of Ni nanoparticles are shown below. Figure 1 and Figure 2 As shown in the figure, the Ni nanoparticles are uniformly dispersed on the support, with a minimum particle size of 3.79 nm, a maximum particle size of 7.47 nm, and an average particle size of 5.45 nm.

[0037] The hydrogen desorption curves of the catalysts prepared in Examples 1-4 of this invention are compared as follows: Figure 3 As shown, the catalysts prepared in Examples 1-4 all have good catalytic hydrogenation activity for the full hydrogenation of N-ethylcarbazole, and can reach or approach the maximum hydrogen release within 60 min. Among them, the catalyst prepared in Example 1 has the best catalytic activity.

[0038] Figure 4 This is a comparison of the hydrogen desorption curves of the catalysts prepared in Example 1 and Comparative Example 1 of this invention, where the catalyst support used in Comparative Example 1 is nano-silica. As can be seen from the figure, the catalyst prepared in Example 1 has significantly better activity than that in Comparative Example 1, which illustrates the importance of support selection, despite the lower specific surface area (160 m²) of nano-silica. 2 / g) is higher than that of γ-alumina powder (140 m 2 However, the catalytically active component Ni can interact with the γ-alumina powder support, thus affecting the catalyst's activity.

[0039] The difference between Comparative Example 2 and Example 1 is that the particle size of the γ-alumina powder carrier was changed from 20 nm to 300 nm. The specific surface area of ​​the γ-alumina powder with a particle size of 20 nm is approximately 140 m². 2 / g, while the specific surface area of ​​γ-alumina powder with a particle size of 300 nm is only 10 m². 2The high specific surface area support provides ample channels for Ni loading and also facilitates the dispersion of Ni nanoparticles. Therefore, the catalyst prepared in Example 1 exhibits significantly better activity than that in Comparative Example 2 (see [example missing]). Figure 5 ).

[0040] The difference between Comparative Example 3 and Example 1 is that the weight of nickel nitrate hexahydrate was changed from 2.5 g to 4.0 g. This indicates that excessive Ni loading is not conducive to the uniform dispersion of Ni nanoparticles and easily causes agglomeration, resulting in the catalyst prepared in Comparative Example 3 having significantly lower activity than that in Example 1 (see Example 1). Figure 6 ).

[0041] The difference between Comparative Example 4 and Example 1 is that the catalyst impregnation and drying method was changed from rotary evaporation drying to vacuum drying oven drying. The corresponding hydrogen desorption curves are compared as follows: Figure 7 As shown, the catalyst prepared in Example 1 exhibits better activity than the catalyst prepared in Comparative Example 4. Characterization revealed that the nanoparticles of the catalyst prepared in Comparative Example 4 showed a certain degree of aggregation (see...). Figure 8 The minimum particle size was 3.92 nm, the maximum particle size was 9.20 nm, and the average particle size was 6.20 nm. This indicates that the choice of drying method is also important and affects catalytic activity.

[0042] The catalyst prepared in Example 1 was subjected to a recycling performance test, and was recycled a total of 5 times. Figure 9 This is a bar chart comparing the hydrogen release of the catalyst prepared in Example 1 after multiple reuses. As can be seen from the figure, there is no significant decrease in the total hydrogen release after 5 cycles, which indicates that the catalyst prepared in Example 1 has good stability. Figure 10 and Figure 11 The images show TEM images and particle size distribution of Ni nanoparticles after repeated use of the catalyst prepared in Example 1. As can be seen from the images, the Ni nanoparticles of the catalyst are still uniformly distributed after repeated testing. The minimum particle size is 5.02 nm, the maximum particle size is 8.48 nm, and the average particle size is 6.65 nm. The average particle size has slightly increased, which indicates that the catalyst has good practicality.

[0043] It should be understood that the above embodiments are for illustrative purposes only and are not intended to limit the present invention. Those skilled in the art can make various modifications or changes based on them. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A Ni-based non-noble metal catalyst, characterized in that: The active component of the catalyst is Ni nanoparticles, and the support is γ-alumina. The loading of Ni nanoparticles is 9.0-20.0%, the particle size of Ni nanoparticles is 3-8 nm, and the particle size of γ-alumina is 20-50 nm.

2. The Ni-based non-noble metal catalyst according to claim 1, characterized in that: The Ni-based non-noble metal catalyst is prepared by the following steps: 1) Weigh γ-alumina powder and add it to deionized water. Disperse it evenly under stirring to obtain γ-alumina dispersion. 2) Weigh out the nickel salt precursor and dissolve it in deionized water to prepare a nickel salt solution; 3) Slowly add the nickel salt solution obtained in step 2) to the γ-alumina dispersion obtained in step 1), and then heat and stir to fully impregnate the γ-alumina carrier to obtain a mixed solution; 4) Transfer the mixture obtained in step 3) to a rotary evaporator for evaporation and dryness, and grind the product to obtain catalyst precursor powder; 5) The catalyst precursor powder obtained in step 4) is reduced at high temperature in a hydrogen atmosphere, and then the product is collected by natural cooling in a hydrogen atmosphere to obtain the Ni-based non-precious metal catalyst.

3. A method for preparing the Ni-based non-noble metal catalyst as described in claim 1, characterized in that: The preparation steps are as follows: 1) Weigh an appropriate amount of γ-alumina powder and add it to deionized water. Disperse it evenly under stirring conditions to obtain a γ-alumina dispersion. 2) Weigh an appropriate amount of nickel salt precursor and completely dissolve it in deionized water to prepare a nickel salt solution; 3) Slowly add the nickel salt solution obtained in step 2) to the γ-alumina dispersion obtained in step 1), and then heat and stir the mixture to fully impregnate the γ-alumina carrier to obtain the mixture. 4) The mixture obtained in step 3) is subjected to rotary evaporation, and the product is ground to obtain catalyst precursor powder; 5) The catalyst precursor powder obtained in step 4) is reduced at high temperature in a hydrogen atmosphere, and then the product is collected by natural cooling in a hydrogen atmosphere to obtain the Ni-based non-precious metal catalyst.

4. The preparation method according to claim 3, characterized in that: The nickel salt precursor mentioned in step 2) is one of nickel nitrate hydrate or nickel acetate hydrate, or a mixture of both.

5. The preparation method according to claim 3, characterized in that: In step 3), the heating and stirring are carried out at a temperature of 40–80°C and a soaking time of 1–5 h; in step 4), the water bath temperature for rotary evaporation is 50–80°C; in step 5), the high-temperature reduction is carried out at a temperature of 400–480°C and a reduction time of 2–4 h, with a heating rate of 3–10°C / min.

6. The application of the Ni-based non-noble metal catalyst as described in claim 1, characterized in that: This catalyst is used for the dehydrogenation of N-ethylcarbazole, which is fully hydrogenated from a liquid organic hydrogen support.

7. The application according to claim 6, characterized in that: The catalyst was mixed with liquid organic hydrogen support N-ethylcarbazole at a mass ratio of 1:

10. The reaction pressure was atmospheric pressure, the reaction temperature was 220℃, and the rotation speed was 100-900 rpm.

Images