Lewis acid catalyzed modified NiZSM-5@LiBH4 composite hydrogen storage material and preparation method thereof

Abstract

The application relates to a Lewis acid catalytic modified NiZSM-5@LiBH4 composite hydrogen storage material and a preparation method thereof. The preparation method comprises the following steps: step one, preparation of a NiZSM-5 Lewis acid catalyst: nickel nitrate hexahydrate, deionized water and diethylenetriamine are added into a reaction kettle; then sodium metaaluminate, n-propyl ammonium hydroxide and deionized water are sequentially added; then tetraethyl orthosilicate is added, stirring and aging are conducted; hydrothermal reaction is carried out under insulation, a reaction product is obtained; the reaction product is washed and dried, and then calcination is carried out in a muffle furnace; reduction is carried out by using hydrogen-argon mixed gas; step two: the NiZSM-5 Lewis acid catalyst is vacuum dried, and then LiBH4 and the NiZSM-5 Lewis acid catalyst are mixed in a glove box after insulation, ball milling is conducted, and a hydrogen storage material is obtained. The composite hydrogen storage material is simple in synthesis, short in period, can effectively improve the hydrogen storage performance of LiBH4, and the hydrogen release capacity reaches 6.4 wt% and 7.8 wt% under isothermal conditions of 350 DEG C and 400 DEG C for 200 min.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of solid-state hydrogen storage materials and its preparation technology, in particular to a Lewis acid catalytic modified NiZSM-5@LiBH4 composite hydrogen storage material and its preparation method. BACKGROUND

[0002] Hydrogen has high energy density, high combustion heat value, clean and pollution-free, abundant storage, and wide sources, etc. It has become an ideal secondary energy in the future. Safe and efficient hydrogen storage is an important and key technology to realize large-scale application of hydrogen energy. The current main hydrogen storage methods include high-pressure gaseous hydrogen storage, liquid hydrogen storage and solid hydrogen storage. High-pressure gaseous hydrogen storage is stored in gaseous state, so it has very high requirements for the pressure resistance and safety of the steel cylinder, and the disadvantage is low hydrogen storage capacity. For liquid hydrogen storage, on the one hand, the cost of converting gaseous hydrogen into liquid hydrogen is high, and on the other hand, liquid hydrogen is easy to gasify, which leads to an increase in the pressure in the container, and puts forward higher requirements for the heat insulation and safety of the low-temperature container. Solid-state hydrogen storage is considered to be the most promising hydrogen storage technology due to its high volume hydrogen storage density and mass hydrogen storage density, and good safety. Among the many solid hydrogen storage materials, light metal borohydride LiBH4 has a high mass hydrogen storage density of 18.5wt% and a volume density of 121kg / m 3 , which is considered to be one of the most promising solid-state hydrogen storage materials.

[0003] Hydrogen storage capacity and dehydrogenation temperature are important factors for measuring the performance of hydrogen storage materials. In recent years, reaction destabilization is one of the important methods to improve the hydrogen storage performance of LiBH4. Reaction destabilization refers to the chemical reaction of adding an additive with LiBH4, which leads to the destabilization of its structure, thereby improving the hydrogen storage performance of LiBH4. However, the existing destabilizing agents mainly use metal oxides, Ti-based compounds and fluorides as additives to improve the hydrogen storage performance of LiBH4. Although the hydrogen storage performance is improved to some extent, it still faces problems such as high dehydrogenation temperature and low hydrogen storage capacity. The essential problem is that these destabilizing agents have limited effect on weakening the electron density between B-H bonds in LiBH4. SUMMARY

[0004] The present application provides a Lewis acid catalytic modified NiZSM-5@LiBH4 composite hydrogen storage material and its preparation method to overcome the problems of high dehydrogenation temperature, high price, difficult preparation and low hydrogen storage performance in the prior art.

[0005] In order to achieve the purpose of the present application, the technical scheme provided by the present application is: a preparation method of a Lewis acid catalytic modified NiZSM-5@LiBH4 composite hydrogen storage material, comprising the following steps:

[0006] Step one, preparation of a NiZSM-5 Lewis acid catalyst:

[0007] (1) First, the nickel nitrate hexahydrate, deionized water, diethylene triamine are added into the reaction kettle and stirred for 20-40 min; then sodium metaaluminate, n-propyl ammonium hydroxide and deionized water are sequentially added into the reaction kettle and stirred at 80-90℃ for 2-3h; then tetraethyl orthosilicate is added and stirred at 80-90℃ for 2-3h, and the reaction is aged to obtain a gel; finally, the reaction is transferred to a forced air drying oven and hydrothermally reacted at 160-180℃ for 48-52h to obtain a reaction product;

[0008] (2) The reaction product is washed, the solution is washed to be neutral, dried at 100℃ for 10h, and then calcined in a muffle furnace at a temperature of 500-580℃ with a heating rate of 2-5℃ / min, and calcined for 4-5h to obtain a NiZSM-5 powder;

[0009] (3) The NiZSM-5 powder is reduced in a tube furnace using hydrogen-argon mixed gas to obtain a NiZSM-5 Lewis acid catalyst;

[0010] Step two: The NiZSM-5 Lewis acid catalyst is vacuum dried at 300-350℃ for 10-12h;

[0011] Step three: In a glove box, the NiZSM-5 Lewis acid catalyst and LiBH4 are mixed according to a mass ratio of 35-50:50-65, placed in a catalyst ball mill jar, then argon gas is filled into the ball mill jar as a protective gas, and the sample is collected after ball milling.

[0012] Further, in the above step one, the nickel nitrate hexahydrate is 0.55-0.6g, the diethylene triamine is 0.16-0.17g, and the deionized water is 20-22g.

[0013] Further, in the above step one, the sodium metaaluminate is 0.1-0.4g, the deionized water is 20-22g, and the n-propyl ammonium hydroxide is 20-22g.

[0014] Further, in the above step one, the tetraethyl orthosilicate is 20-22g.

[0015] Further, the above Si / Al molar ratio is 25-50:1.

[0016] Further, in the above step one, the reduction step is: the sample is reduced in a tube furnace using a mixed gas with a volume percentage of 10% H2+90% Ar, and is kept at 400-500℃ for 2-3h and then heated to 550-600℃ for 3-4h.

[0017] Further, in the above-mentioned step three, the NiZSM-5 Lewis acid catalyst and LiBH4 are mixed in a mass ratio of 4:6 in a glove box.

[0018] Further, in the above-mentioned step three, the ball milling jar has a capacity of 220 ml, the ball-to-material ratio is 100:1, and the carbide beads used have a diameter of 6 mm.

[0019] Further, the composite hydrogen storage material prepared by the above-mentioned preparation method.

[0020] Compared with the prior art, the present application has the following advantages:

[0021] 1. In the synthesis process, metal monatomic nickel is first introduced in situ, and the NiZSM-5 powder obtained through aging and hydrothermal treatment is directly reduced by using hydrogen-argon mixed gas to obtain the NiZSM-5 Lewis acid catalyst. In this process, the hydrogen-argon mixed gas can cause the redox reaction of the NiZSM-5, so that the Ni in the NiZSM-5 is embedded in the framework in the form of monatomic Ni. The existence of these monatomic Ni can act as a destabilizing agent to improve the hydrogen storage performance of LiBH4.

[0022] 2. In the synthesis process, the introduction of metal monatomic Ni acts as a Lewis acid active site, so that the prepared NiZSM-5 Lewis acid catalyst has abundant Lewis acid active sites. In the preparation process, the number of Lewis active sites can be regulated by changing the Si / Al molar ratio. The smaller the Si / Al ratio, the stronger the acidity of the obtained NiZSM-5 Lewis acid catalyst. When the NiZSM-5 Lewis acid catalyst is introduced into the hydrogen storage material, these Lewis acid active sites in the NiZSM-5 can attract electrons, so as to weaken the electron cloud density between the B-H bonds in LiBH4. The NiZSM-5 Lewis acid catalyst is considered to be an electron pair acceptor. The NiZSM-5 of the present application has abundant Lewis acid sites. The more the number of acid sites, the stronger the acidity, and the stronger the ability to accept electrons. In the composite system composed of the NiZSM-5 and LiBH4, the Lewis acid sites of the NiZSM-5 Lewis acid catalyst interact with the electrons between the B-H bonds in LiBH4, weakening the electron cloud density between the B-H bonds in LiBH4, and causing the structural instability of LiBH4.

[0023] 3. The application uses NiZSM-5 Lewis acid catalyst as an additive to prepare a composite hydrogen storage material, so that the composite hydrogen storage material can be prepared by a simple ball milling process, and the hydrogen storage performance is high. The metal monatomic introduced in the application can act as a destabilizing agent to reduce the hydrogen release temperature of LiBH4. The starting hydrogen release temperature of the composite hydrogen storage material of the application is reduced by 75 DEG C compared with the original LiBH4, and the hydrogen release capacity can reach 7wt% when heated to 450 DEG C. Compared with the original LiBH4, the hydrogen release performance has been greatly improved. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is the Xrd characterization of NiZSM-5 (Si / Al = 50, 200).

[0025] Figure 2 is the infrared pyridine absorption spectrum of NiZSM-5 (Si / Al = 50, 200) qualitative Lewis acid at different temperatures.

[0026] Figure 3 is the SEM characterization of NiZSM-5 (Si / Al = 50).

[0027] Figure 4 is the non-isothermal dehydrogenation graph of 6LiBH4@4NiZSM-5 (Si / Al = 50) composite system.

[0028] Figure 5 is the isothermal hydrogen release graph of 6LiBH4@4NiZSM-5 (Si / Al = 50) composite hydrogen storage system at 350 DEG C, 400 DEG C. DETAILED DESCRIPTION

[0029] The application will be described in detail below in conjunction with the drawings and examples.

[0030] Example 1: A preparation method of a Lewis acid catalytic modified NiZSM-5@LiBH4 composite hydrogen storage material, the specific steps are as follows:

[0031] Step one: preparation of NiZSM-5 Lewis acid catalyst:

[0032] (1) weigh 0.582g of nickel nitrate hexahydrate, 0.168g of diethylene triamine, 20.376g of deionized water into a 100ml hydrothermal reactor, and stir at room temperature for 30min. Then weigh 0.164g of sodium metaaluminate, 20.376g of water, 20.336g of tetrapropylammonium hydroxide respectively, and put them into the reactor, and stir at 80 DEG C for 2h, then add 20.838g of tetraethyl orthosilicate, and stir at 80 DEG C for 3h, and age. After aging, transfer to a forced air drying oven, react at 180 DEG C for 48h, and obtain the reaction product.

[0033] (2) The reactants were washed with deionized water, at least 3 times, to wash the solution to neutral. The sample was placed in a crucible, dried at 100°C for 10h, and after drying, placed in a muffle furnace at 550°C (heating rate 2°C / min) calcination for 4h to remove the organic template, to obtain the sample.

[0034] (3) The sample was reduced in a tube furnace, using hydrogen argon mixed gas (10% H2+90% Ar), at 400°C for 2h and then heated to 550°C for 4h. The sample NiZSM-5(Si / Al=50) catalyst was obtained after the tube furnace cooled down.

[0035] Step two: The NiZSM-5(Si / Al=50) catalyst was dried in a vacuum oven at 300°C for 12h before use, to remove the adsorbed water and impurity gases.

[0036] Step three: In a glove box, 0.6g of LiBH4and 0.4g of NiZSM-5(Si / Al=50) catalyst were weighed into a ball mill jar with a volume of 220ml, and carbide beads with a diameter of 6mm were placed in the ball mill jar to ensure a ball-to-material ratio of 100:1. Then argon was filled in the ball mill jar as a protective gas. The ball mill jar was placed in a ball mill, set to a two-way mode, a rotation speed of 400rpm, a positive and negative rotation of 30min each, a time interval of 6min, and a running number of 2 times.

[0037] The collected product was a 6LiBH4@4NiZSM-5(Si / Al=50) composite hydrogen storage material.

[0038] The prepared 6LiBH4@4NiZSM-5 composite hydrogen storage system was subjected to non-isothermal testing. The non-isothermal performance testing instrument was a Sieverts-type gas-solid reaction device from Zhejiang University. The sample amount loaded each time was 50mg, and the sample was connected to the large instrument. Vacuum was performed, and the non-isothermal testing program was set while vacuuming. After vacuuming was completed, 10min was waited, and non-isothermal testing was performed.

[0039] Referring to Figure 4 , the test results showed that the initial hydrogen release temperature of the 6LiBH4@4NiZSM-5 composite system was reduced by 75°C compared to the original LiBH4, and the hydrogen release capacity could reach 7wt% when heated to 450°C. The NiZSM-5(Si / Al=50) catalyst can effectively weaken the B-H bond in LiBH4, and the hydrogen release performance is greatly improved compared to the original LiBH4.

[0040] Referring to Figure 5The prepared 6LiBH4@4NiZSM-5 (Si / Al=50) composite hydrogen storage system was subjected to isothermal tests at 350℃ and 400℃. Each test used 50mg of sample, which was connected to the instrument. Vacuum was applied, and the isothermal test program could be set simultaneously with the vacuum process. After vacuuming, the isothermal test was performed after 10 minutes. The test results showed that the hydrogen release after 100 minutes of isothermal treatment at 350℃ and 400℃ (including the heating time, from room temperature to the target temperature at a rate of 10℃ / min) reached 6.4wt% and 7.8wt%, respectively.

[0041] Examples 2-4 illustrate a method for preparing a Lewis acid-catalyzed NiZSM-5@LiBH4 composite hydrogen storage material, with the following specific steps:

[0042] Step 1: The preparation method of the NiZSM-5 (Si / Al = 25, 100, 200) Lewis acid catalyst is the same as in Example 1, except that the Si / Al ratio is different, which is achieved by changing the amount of sodium aluminate added. The amounts of raw materials added are shown in Table 1:

[0043] Table 1

[0044]

[0045] Step 2: The NiZSM-5 (Si / Al = 25, 100, 200) Lewis acid catalysts prepared with different parameters as described in steps 2-4 above were placed in a vacuum oven at 350°C for 10 hours to remove adsorbed water and impurity gases.

[0046] Step 3: Weigh 0.6g of LiBH4 and 0.4g of NiZSM-5 (Si / Al = 25, 100, 200) catalyst in a glove box and place them into a 220ml ball mill jar. Add 6mm diameter carbide beads to the jar, ensuring a ball-to-material ratio of 100:1. Then, purge the jar with argon gas as a protective gas. Place the jar in a ball mill, set to bidirectional mode, speed of 450rpm, and run in both directions for 15 minutes each, with a 6-minute interval, repeating the cycle twice.

[0047] The collected products were 6LiBH4@4NiZSM-5 (Si / Al = 25, 100, 200) composite hydrogen storage materials.

[0048] The prepared 6LiBH4@4NiZSM-5 (Si / Al=200) composite hydrogen storage system was subjected to non-isothermal testing. It was found to be 50℃ lower than the original LiBH4, and the hydrogen release capacity could reach 6.4wt% when heated to 450℃.

[0049] The prepared 6LiBH4@4NiZSM-5 (Si / Al=200) composite hydrogen storage system was subjected to isothermal tests at 350℃ and 400℃. The test results showed that the hydrogen release rate reached 5.8wt% and 6.2wt% respectively after 100 min of isothermal testing at 350℃ and 400℃ (including the heating time, from room temperature to the target temperature at a rate of 10℃ / min).

[0050] See Figure 1 As can be seen, NiHZSM-5 (Si / Al = 50, 200) has the same MFI crystal structure and belongs to the orthorhombic system. The in-situ introduction of a single Ni atom does not change the crystal structure.

[0051] Infrared semi-quantitative analysis of pyridine was performed on two NiZSM-5 Lewis acid catalysts with different Si / Al ratios (Si / Al = 50 and 200). As shown in Table 2, Si / Al = 50 has more Lewis acid sites.

[0052] Table 2

[0053]

[0054] See Figure 2 The spectrum shows that Si / Al=50 has a stronger Lewis acid, which means that it contains more Lewis acid.

[0055] See Figure 3 As can be seen from the figure, NiZSM-5 has an ordered and regular cubic shape, exhibiting uniform crystal grains.

[0056] Example 1 in the above embodiments is the best embodiment.

[0057] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the embodiments described above. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a Lewis acid-catalyzed NiZSM-5@LiBH4 composite hydrogen storage material, characterized in that... Includes the following steps Step 1: Preparation of NiZSM-5 Lewis acid catalyst: (1) First, nickel nitrate hexahydrate, deionized water, and diethylenetriamine were added to the reactor and stirred for 20-40 min. Then, sodium aluminate, n-propylammonium hydroxide, and deionized water were added to the reactor in sequence and stirred at 80-90 °C for 2-3 h. Then, tetraethyl orthosilicate was added and stirred at 80-90 °C for 2-3 h. After aging, the reactants were used to obtain gels. Finally, the gels were transferred to a forced-air drying oven and kept at 160-180 °C for 48-52 h for hydrothermal reaction to obtain the reactants. (2) Wash the reactants to make the solution neutral, dry it at 100 °C for 10 h, and then calcine it in a muffle furnace at 500-580 °C with a heating rate of 2-5 °C / min for 4-5 h to obtain NiZSM-5 powder. (3) NiZSM-5 powder was reduced in a tube furnace using a hydrogen-argon mixture to obtain NiZSM-5 Lewis acid catalyst; Step 2: Vacuum dry the NiZSM-5 Lewis acid catalyst and keep it at 300-350 ℃ for 10-12 h; Step 3: Mix NiZSM-5 Lewis acid catalyst and LiBH4 in a glove box at a mass ratio of 35-50:50-65, place the mixture in a catalyst ball mill jar, and then fill the ball mill jar with argon gas as a protective gas. After ball milling is completed, collect the sample.

2. The preparation method of the Lewis acid-catalyzed NiZSM-5@LiBH4 composite hydrogen storage material according to claim 1, characterized in that, In step one, the amount of nickel nitrate hexahydrate is 0.55-0.6g, the amount of diethylenetriamine is 0.16-0.17g, and the amount of deionized water is 20-22g.

3. The preparation method of the Lewis acid-catalyzed NiZSM-5@LiBH4 composite hydrogen storage material according to claim 2, characterized in that, In step one, the amount of sodium aluminate is 0.1-0.4g, the amount of deionized water is 20-22g, and the amount of n-propylammonium hydroxide is 20-22g.

4. The preparation method of the Lewis acid-catalyzed NiZSM-5@LiBH4 composite hydrogen storage material according to claim 3, characterized in that, In step one, the amount of tetraethyl orthosilicate is 20-22g.

5. The method for preparing the Lewis acid-catalyzed NiZSM-5@LiBH4 composite hydrogen storage material according to any one of claims 1-4, characterized in that, The Si / Al molar ratio is 25-50:

1.

6. The preparation method of the Lewis acid-catalyzed NiZSM-5@LiBH4 composite hydrogen storage material according to claim 1, characterized in that, In step one, the reduction step is as follows: the sample is reduced in a tube furnace using a mixed gas with a volume percentage of 10% H2 and 90% Ar, and held at 400-500℃ for 2-3 h, then heated to 550-600℃ and held for 3-4 h.

7. The preparation method of the Lewis acid-catalyzed NiZSM-5@LiBH4 composite hydrogen storage material according to claim 6, characterized in that, In step three, the NiZSM-5 Lewis acid catalyst and LiBH4 are mixed in a glove box at a mass ratio of 4:

6.

8. The preparation method of the Lewis acid-catalyzed NiZSM-5@LiBH4 composite hydrogen storage material according to claim 7, characterized in that, In step three, the capacity of the ball mill jar is 220ml, the ball-to-material ratio is 100:1, and the grinding beads used are carbide beads with a diameter of 6mm.

9. The composite hydrogen storage material prepared by the method according to claim 1.

Images