CN101920973B

CN101920973B - Method for preparing porous aluminum diboride

Info

Publication number: CN101920973B
Application number: CN2010102698946A
Authority: CN
Inventors: 陈如柑; 王新华; 陈立新; 李寿权; 葛红卫; 陈长聘
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2010-09-02
Filing date: 2010-09-02
Publication date: 2012-06-27
Anticipated expiration: 2030-09-02
Also published as: CN101920973A

Abstract

The invention discloses a method for preparing porous aluminum diboride (AlB2). The porous AlB2 is prepared from LiAlH4 and LiBH4 serving as raw materials, wherein the molar ratio of the LiAlH4 to the LiBH4 is 1:1-1:3. Through the method, the LiAlH4 is used as an initial raw material instead of pure Al and is heated and decomposed to generate Al particles with high degree of dispersion; and as the particles do not contain any oxide coating, the particles have remarkably high activity. Moreover, the AlB2 prepared by reacting the LiAlH4 instead of the Al with the LiBH4 is porous powder, the specific area is increased, and a channel for hydrogen to disperse from the surface toward the inside is provided, so the hydrogen absorption dynamic performance of the AlB2 is obviously improved.

Description

A kind of preparation method of porous aluminum diboride

Technical field

The present invention relates to the preparation field of porous metal compound, be specifically related to a kind of preparation method of porous aluminum diboride.

Background technology

Hydrogen Energy is a kind of green, the reproducible energy, has a good application prospect.But Hydrogen Energy is before being able to widespread use, at first will search out the material of a large amount of hydrogen gas storages of a kind of ability.As a kind of new type of metal complex hydrides, lithium borohydride (LiBH ₄) the Theoretical Mass hydrogen-storage density up to 18.3%, can satisfy the application demand that moves the storage hydrogen carrier well.But, LiBH ₄Reversal condition harsh, lithium hydride (LiH) and pure boron (B) need just can react generation LiBH under the hydrogen condition of 600 ℃ and 35MPa ₄Intermetallic compound be meant metal and metal or and metalloid element between the compound that forms; Bibliographical information, intermetallic compound AlB ₂Under comparatively gentle condition, can generate LiBH with LiH and hydrogen reaction ₄(Friedrichs O, Kim JW, Remhof A, Buchter F, Borgschulte A, Wallacher D, Cho YW, Fichtner M, Oh KH, Zuttel A.Theeffect of Al on the hydrogen sorption mechanism of LiBH ₄.PhysicalChemistry Chemical Physics, 2009 (11) 1515-1520).Present research shows that the diffusion of hydrogen is restriction LiBH ₄The regenerated principal element.Thereby, prepare AlB with vesicular structure ₂, to improving LiBH ₄Regenerative power is learned performance and is had material impact.

Pure aluminum and boron generate AlB ₂Eutectic temperature be about 980 ℃.The fusing point of Al is about 660 ℃, far below 2027 ℃ of the fusing points of B, because fusing point difference great disparity prepares AlB through the fused method ₂Feasibility is not high.Existing bibliographical information, pure aluminum and lithium borohydride can react and generate AlB ₂(DjordjeMirkovic; Joachim Grobner; Rainer Schmid-Fetzer, Olga Fabrichnaya, HansLeo Lukas; Experimental study and thermodynamic re-assessment of Al-Bsystem.Journal of Alloys and Compounds, 384 (2004) 168-174.).Usually, common Al particle top layer is coated with the fine and close sull of one deck, and it is active seriously to have reduced the Al particulate; Simultaneously because common Al particulate granularity is bigger, disperse inhomogeneous, thereby can not same well LiBH ₄Reaction generates AlB ₂

Summary of the invention

The invention provides a kind of preparation method of porous aluminum diboride, this method is simple to operate, is suitable for suitability for industrialized production.

A kind of preparation method of porous aluminum diboride comprises:

With lithium aluminum hydride (LiAlH ₄) and lithium borohydride (LiBH ₄) be raw material, preparation has the aluminium diboride (AlB of vesicular structure ₂); Described LiAlH ₄And LiBH ₄Mol ratio be 1: 1～1: 3.

The present invention finds to have the AlB of vesicular structure ₂Can improve LiAlH well ₄-LiBH ₄Compound system is put the speed that the hydrogen sample is inhaled hydrogen again.If LiBH ₄Amount very little, the AlB that then generates ₂Porosity will reduce; On the contrary, if LiBH ₄Amount too much, unnecessary B then is coated on the powder particle skin, can not generate this vesicular structure equally.

In order to economize on resources, and reach effect better, preferred:

Described porous Al B ₂The preparation method, specifically comprise step:

(1) with LiAlH ₄And LiBH ₄After the mixing, mechanical ball milling mixes it under protection of inert gas, obtains LiAlH ₄And LiBH ₄Mixture;

(2) to above-mentioned LiAlH ₄And LiBH ₄Feed hydrogen in the mixture, be warming up to 450 ℃～550 ℃ (preferred 500 ℃), make AlB with vesicular structure ₂

In the step (1), the time of mechanical ball milling is 4.5h～5.5h, further preferred 5h.

Described rare gas element comprises the rare gas element in the broad scope of this area, generally selects a kind of in nitrogen, helium, the argon gas etc. for use.

In the step (2), the temperature rise rate during intensification is 1 ℃/min～5 ℃/min.

The pressure of described hydrogen is 2atm～5atm; The pressure of hydrogen is too low, the more difficult same LiBH of Al ₄React and generate AlB ₂The pressure of hydrogen is too high, LiBH ₄Decomposition temperature is too high, AlB ₂Productive rate reduce equally.

Porous Al B of the present invention ₂Under 400 ℃～500 ℃ (preferred 450 ℃) and 7MPa～10MPa (preferred 8MPa) hydrogen pressure, inhale hydrogen again, can generate LiBH ₄General adopt existing method, as with AlB ₂With LiH be raw material, in hydrogen, react, make the LiBH of hydrogen gas storage ₄Concrete reaction equation is following:

AlB ₂+2LiH+3H ₂→2LiBH ₄+Al

Compared with prior art, the present invention has following advantage:

The present invention uses LiAlH ₄Instead of pure Al is as initial feed, LiAlH ₄Decomposes will produce the Al particle of high diffusive degree, because these particles do not contain the oxide compound coating layer, thereby have very high activity.In addition, with LiAlH ₄Substitute for Al and LiBH ₄The AlB of prepared in reaction ₂Be a kind of body of powder, also passage be provided when increasing reference area, thereby significantly improved AlB for hydrogen diffusion from the surface to the internal with vesicular structure ₂Suction hydrogen dynamic performance.

Description of drawings

Fig. 1 is the X ray diffracting spectrum of different steps product among the embodiment 1;

Fig. 2 is the AlB of embodiment 1 preparation ₂Suction hydrogen curve;

Fig. 3 is the AlB of embodiment 4 preparations ₂Microscopic appearance figure;

Fig. 4 is the AlB of embodiment 5 preparations ₂Microscopic appearance figure;

Fig. 5 is the AlB of embodiment 6 preparations ₂Microscopic appearance figure;

Fig. 6 is the AlB of Comparative Examples 1 preparation ₂Microscopic appearance figure.

Embodiment

In following each embodiment and the Comparative Examples, productive rate is meant AlB ₂Shared weight percentage in product.

Embodiment 1

With LiAlH ₄, LiBH ₄Be 1: 2 mixed in molar ratio, put into a stainless steel jar mill together with hard ball, feed argon gas as protection gas, mechanical ball milling mixed it in 5 hours.The mixture that mechanical ball milling is good joins reactor drum, feeds the hydrogen of 2atm, progressively is heated to 500 ℃ with the temperature rise rate of 1 ℃/min, makes the AlB with vesicular structure ₂, its productive rate is 72.1%, from its microscopic appearance figure, finds out the AlB that makes ₂Has vesicular structure.

With the above-mentioned AlB for preparing ₂And LiH (AlB ₂With the mol ratio of LiH be 1: 2) under 450 ℃ and 8MPa hydrogen pressure, inhale hydrogen again, generate LiBH ₄

The X ray diffracting spectrum of the mixture that above-mentioned mechanical ball milling is good has the AlB of vesicular structure shown in Fig. 1 (a) ₂X ray diffracting spectrum shown in Fig. 1 (b), AlB ₂Again inhale the LiBH that hydrogen generates ₄X ray diffracting spectrum shown in Fig. 1 (c).Above-mentioned AlB ₂Suction hydrogen curve such as Fig. 2.

Can know LiAlH by Fig. 1 (b) ₄Decompose to produce evenly, the Al particle of disperse fully and LiBH ₄React, the product that obtains at last is the higher AlB of purity ₂

Can know the AlB for preparing by Fig. 1 (c) ₂Generated LiBH after under 450 ℃ and 8MPa condition, inhaling hydrogen ₄, this generates LiBH far below LiH and pure boron reaction ₄Required 600 ℃ and the condition of 35MPa hydrogen pressure.

Can know the AlB of this vesicular structure by Fig. 2 ₂Have quick hydrogen-absorbing ability, preceding 50 minutes hydrogen (weight percentage) is that 4.88%, 600 minute hydrogen (weight percentage) is 6.80%.

Embodiment 2

With LiAlH ₄, LiBH ₄Be 1: 2 mixed in molar ratio, put into a stainless steel jar mill together with hard ball, feed nitrogen as protection gas, mechanical ball milling mixed it in 5 hours.The mixture that mechanical ball milling is good joins reactor drum, feeds the hydrogen of 3.5atm, progressively is heated to 500 ℃ with the temperature rise rate of 5 ℃/min, makes the AlB with vesicular structure ₂, its productive rate is 72.8%, from its microscopic appearance figure, finds out the AlB that makes ₂Has vesicular structure.

The preceding 50 minutes hydrogen (weight percentage) of this sample is that 5.02%, 600 minute hydrogen (weight percentage) is 6.97%.

Embodiment 3

With LiAlH ₄, LiBH ₄Be 1: 2 mixed in molar ratio, put into a stainless steel jar mill together with hard ball, feed argon gas as protection gas, mechanical ball milling mixed it in 5 hours.The mixture that mechanical ball milling is good joins reactor drum, feeds the hydrogen of 5atm, progressively is heated to 500 ℃ with the temperature rise rate of 3 ℃/min, makes the AlB with vesicular structure ₂, its productive rate is 71.6%, from its microscopic appearance figure, finds out the AlB that makes ₂Has vesicular structure.

The preceding 50 minutes hydrogen (weight percentage) of this sample is that 4.95%, 600 minute hydrogen (weight percentage) is 6.93%.

Embodiment 4

With LiAlH ₄, LiBH ₄Be 1: 1 mixed in molar ratio, put into a stainless steel jar mill together with hard ball, feed argon gas as protection gas, mechanical ball milling mixed it in 5 hours.The mixture that mechanical ball milling is good joins reactor drum, feeds the hydrogen of 2atm, progressively is heated to 500 ℃ with the temperature rise rate of 3 ℃/min, makes the AlB with vesicular structure ₂, its productive rate is 45.8%, figure is as shown in Figure 3 for its microscopic appearance, shows the AlB that makes ₂Has vesicular structure.

The preceding 50 minutes hydrogen (weight percentage) of this sample is that 3.66%, 600 minute hydrogen (weight percentage) is 4.41%.

Embodiment 5

With LiAlH ₄, LiBH ₄Be 1: 2 mixed in molar ratio, put into a stainless steel jar mill together with hard ball, feed argon gas as protection gas, mechanical ball milling mixed it in 5 hours.The mixture that mechanical ball milling is good joins reactor drum, feeds the hydrogen of 2atm, progressively is heated to 500 ℃ with the temperature rise rate of 3 ℃/min, makes the AlB with vesicular structure ₂, its productive rate is 71.7%, figure is as shown in Figure 4 for its microscopic appearance, shows the AlB that makes ₂Has vesicular structure.

The preceding 50 minutes hydrogen (weight percentage) of this sample is that 4.69%, 600 minute hydrogen (weight percentage) is 6.74%.

Embodiment 6

With LiAlH ₄, LiBH ₄Be 1: 3 mixed in molar ratio, put into a stainless steel jar mill together with hard ball, feed argon gas as protection gas, mechanical ball milling mixed it in 5 hours.The mixture that mechanical ball milling is good joins reactor drum, feeds the hydrogen of 2atm, progressively is heated to 500 ℃ with the temperature rise rate of 3 ℃/min.Because unnecessary B covers AlB ₂The surface, the AlB that makes ₂Vesicular structure is not obvious, and its productive rate is 48.2%, and figure is as shown in Figure 5 for its microscopic appearance.

The preceding 50 minutes hydrogen (weight percentage) of this sample is that 5.41%, 600 minute hydrogen (weight percentage) is 5.88%.

Comparative Examples 1

With Al, LiBH ₄Be 1: 2 mixed in molar ratio, put into a stainless steel jar mill together with hard ball, feed argon gas as protection gas, mechanical ball milling mixed it in 5 hours.The mixture that mechanical ball milling is good joins reactor drum, feeds the hydrogen of 2atm, progressively is heated to 500 ℃ with the temperature rise rate of 3 ℃/min, makes blocky AlB ₂, its productive rate is 8.1%, and figure is as shown in Figure 6 for its microscopic appearance, and X ray diffracting spectrum is shown in Fig. 1 (d).

The above-mentioned AlB that obtains ₂Be a kind of lumphy structure, can know: because most Al particle and have neither part nor lot in reaction, LiBH from Fig. 6 ₄Decompose the pure boron and the LiH that produce and be coated on Al particle top layer, form loose coating layer.

Can know from Fig. 1 (d), with Al and LiBH ₄Can only obtain a spot of AlB by 1: 2 molar ratio reaction ₂, this is because the Al particle size is bigger, disperses inhomogeneously, and simultaneously there is oxide skin on the top layer, and the lower reason of activity causes.

The preceding 50 minutes hydrogen (weight percentage) of this sample is that 0.7%, 600 minute hydrogen (weight percentage) is 1.2%.

Claims

1. porous Al B ₂The preparation method, comprising: with LiAlH ₄And LiBH ₄Be raw material, preparation has the AlB of vesicular structure ₂Described LiAlH ₄And LiBH ₄Mol ratio be 1: 1～1: 3;

(1) with LiAlH ₄And LiBH ₄After the mixing, mechanical ball milling mixes it under a kind of protection in nitrogen, helium, argon gas, obtains LiAlH ₄And LiBH ₄Mixture;

The time of mechanical ball milling is 4.5h～5.5h;

(2) to above-mentioned LiAlH ₄And LiBH ₄Feed hydrogen in the mixture, be warming up to 450 ℃～550 ℃, make AlB with vesicular structure ₂

Temperature rise rate during intensification is 1 ℃/min～5 ℃/min;

The pressure of described hydrogen is 2atm～5atm.