Lithium hydride

hello everyone, i am thinking about buying bulk industrial grade LiH as an easy portable hydrogen source when reacted with water, the theoretical yield of H2 is roughly 3 m3/ kg, very probably its the chemical reaction with the largest volume change - its so large that a very light baloon filled with stoichiometrical proportions of water and LiH considering 100% conversion to LiOH and H2 should lift this baloon in air without dropping any weight. however, the heat of reaction is still quite high what is a littlebit wasteful

the literature says lithium should easily pick up hydrogen at 600-700°C with conversion up to 99% in an iron crucible, but i have no time to learn this preparation for test purposes only and also i think somebody produces this stuff for a fair price and in bulk form-i mean chunks, granules, not powder-the reaction of powder with water is too fast. could anybody help me find out from where to order LiH for a fair price???, i searched google and alibaba but the results are not promissing. if the price would be low enough (maximum tenths of dollars/kg) i would buy some 10 kg-100kg

the dark side of the stuff: some literature says alkali metal hydrides are pyrophoric on air - it may classify this idea unpractical, but i tested some old LiH(only 30% LiH content based on H2 volume generated, rest was already converted to Li2CO3 and LiOH) and this fine material didnt ignite on air, also not in the test-tube at the beginning of water adition, so i hope that this kind of H2 generation could be feasible and maybe even safe enough to avoid any unwanted ignition of the prepared hydrogen.

avaiting any response on LiH source

LiBH4 is a nice idea, i always thought that borohydrides naturally release diborane and hydrogen in the 1:1 ratio by water hydrolysis, so i never calculated the hydrogen yield, wikipedia says that upon using a metal catalyst, borohydride solution gives off hydrogen, and the other product should be the alkali borate:

"In the presence of metal catalysts, sodium borohydride releases hydrogen. Exploiting this reactivity, sodium borohydride is used in prototypes of the direct borohydride fuel cell. The hydrogen is generated for a fuel cell by catalytic decomposition of the aqueous borohydride solution:
NaBH4 + 2 H2O → NaBO2 + 4 H2 (ΔH < 0)"

but it also says that diborane can be also formed:

"Sodium borohydride is a source of basic borate salts which can be corrosive, and hydrogen or diborane, which are both flammable. Spontaneous ignition can result from solution of sodium borohydride in dimethylformamide"

i would not like any diborane in my H2, i would be afraid about the pyrophoricity of such mixture

but, really, LiBH4 under standard conditions should theoretically give up to 4,4 m3 H2/kg(i hope nobody will come with a reaction with even higher volume change ) if reacted with water, but if NaBH4 is so widely available, with its yield of roughly 2,5 m3/kg i would be absolutelly satisfied as with a H2 source, so the question is whether it could be decomposed selectively enough only to hydrogen an borate without or with minimal diborane release, and, again the safety and form of the product(i would prefer again bulk against powder)

Quote: Originally posted by deltaH

Have you considered the reaction: Al(s) + 3H2O(l) + NaOH(aq) => NaAl(OH)4(s) + 1.5H2(g) It's cheap as hell and completely OTC. Granted, it only produces 1/3 as much hydrogen as LiH on a weight basis, but still...

Quote: Originally posted by zed

Well, some used hydrogen generated from LiH, but CaH2 probably does a better job, and it is easier to handle. It also used to be cheap as dirt, on-line. Not so any longer. ... Could make your own, via the hydrogenation of Calcium Carbide. Seems do-able. And, economical. https://www.jstage.jst.go.jp/article/jinstmet1952/58/3/58_3_... There is a PDF of the Paper, available on site. Somewhere on this board there is a link to a pretty good paper/patent on the topic. This is actually very old information. Dig. http://www.ebay.com/itm/Calcium-carbide-2-pound-mole-root-vo... Probably cheaper somewhere.

Launched into orbit is more like it

Quote: Originally posted by deltaH

Al(s) + 3H2O(l) + NaOH(aq) => NaAl(OH)4(s) + 1.5H2(g) Granted, it only produces 1/3 as much hydrogen as LiH on a weight basis, but still...

This is what I do. Sometimes HCl + Zn.
I prefer to use the HCl + metal because depending on the metal, I can control the rate of bubbling. With a tweaked concentration of HCl and Iron shavings, one could theoretically continuously generate hydrogen gas for a week.

Alkali Metal Hydrides are a great in-situ hydrogen source. But then again, so is Ammonium Formate which should be cheaper.

Remember that during a gas generation, sealed atmosphere, one must use a pressure equalising funnel. I've had so many mishaps with simple addition funnels, hehe

Quote: Originally posted by dermolotov

... Alkali Metal Hydrides are a great in-situ hydrogen source. But then again, so is Ammonium Formate which should be cheaper. ...

Quote: Originally posted by careysub

Quote: Originally posted by dermolotov   ... Alkali Metal Hydrides are a great in-situ hydrogen source. But then again, so is Ammonium Formate which should be cheaper. ... What is the procedure for generating hydrogen gas from ammonium formate?

Quote: Originally posted by JJay

You can generate alkali metal hydrides in the lab by directly combining alkali metal with hydrogen at high temperatures (around 700 C) at slight pressure. Pressure isn't really necessary but does keep air out of the apparatus and speeds the reaction. Bauer's two-volume handbook in the Sciencemadness library gives some details. [Edited on 9-1-2016 by JJay]