muze801 - 11-1-2009 at 18:46
I am trying to do some research to explore the possibilities of NaBH4 for H2 storage in a fuel cell system for a school related project.
I am familiar with the Brown-Schlesinger process, but am wondering if anyone on the forum is familiar with this and other processes.
I'm also curious about simplifying the Brown-Schlesinger (ie. a simpler was of making NaH?)
If anyone has experience or insight on this, I would appreciate any information (including references).
Sauron - 11-1-2009 at 19:27
First of all there is literature aplenty on the manufacture of NaBH4 by a variety of processes, some of which do not involve metal hydrides.
See Brauer's Handbbok of Preparative Inorganic Chemistry in forum library downloadable for the modest price of $0.00
Also the patent literature, Google, freepatentsonline.com etc
There's an article in Industrial & Engineering Chemistry on manufacture of KBH4.
NaBH4 is bot the one you want for reversible H2 storage. Ca(BH4)2 is preferred for that as you would know if you googled the matter. And it is made by
simple metathesis with NaBH4 (2 mols) and CaCl2 (anhydrous) in Et2O or THF. A older patent advises using DMF or another amine as solvent but the
complexes thus formed are difficult to break up. The calcium borohydride-bis(THF) complex breaks up at 130 C in vacuo leaving the anhydrous compound.
If you use the forum search engine you will find a recent thread on this subject with links to journal articles of interest. The thread was mine. So I
won't have to repeat myself.
chemoleo - 11-1-2009 at 20:13
Sauron, please point out the link to the thread, and I can merge this one, or close it.
PS Are you referring to this?
https://sciencemadness.org/talk/viewthread.php?tid=11636
Seems this is about Ca/Ba borohydrides.
Is there a thread specifically about NaBH4?
[Edited on 12-1-2009 by chemoleo]
sparkgap - 11-1-2009 at 20:43
chemoleo, may I suggest just merging the threads and renaming the thread to "Metal Borohydrides" or something like it. I gathered from the lit Sauron
asked me to retrieve that most of them need nothing fancier than metathesis anyway... 
sparky (~_~)
Sauron - 11-1-2009 at 21:07
My targets were the alkali earth borohydrides, but in order to make them you need LiBH4 or NaBH4 and so in that thread I posted and discussed all of
those.
Yes that is the thread I was referring to. The point is, this thread is only a couple of weeks old and this newbie has not used the FSE, nor Google
nor the forum library so just how much spoonfeeding do you reckon he deserves? Let him do his own paper chase. It's a school project. I figure they
are trying to teach him how to research a topic, so let him learn.
The early preps of the alkali borohydrides relied on boron trihalide-etherates, trialkoxy borates, etc and an alkali hydride. Diborane was also used.
Later processes that do not involve metal hydrides do require very high pressures and temperatures well beyond those compatible eith typical lab
autoclaves and so are merely of industrial significance. These are usually found only in the patent literature.
This student is no more likely to simplify the prep of any borohydride in a novel fashion than he is to build a fuel cell. He's just writing a report.
What I am saying is nothing more than what Nicodem has been saying over and over till he is blue in the face. A modicum of demonstrated attempt at
scholarship must precede the posting of a request for assistance if such a request is to be taken seriously.
In that light I think directing this young man as I did was more than generous.
[Edited on 12-1-2009 by Sauron]
muze801 - 11-1-2009 at 23:41
Sauron,
Thanks for the reply, it did help me find some things that I had overlooked. That said, I have done a significant amount of "paper chasing" and have
hundred of pages of pdf's of patents, articles, and other papers related to my project that I have found. Admittedly, I did not search this site as I
should have prior to posting.
Regarding the nature of my project, I do not plan on, or expect to devise any novel or magical borohydride syntheses, but just mean to explore the
advancements that have been made, and the areas there are for improvement. Unfortunately I do not have an extensive chemical knowledge base, as most
of my time is spent dabbling in electronics, however I am trying to expand my horizons somewhat.
This is not a school assigned project, rather I have it taken upon myself to start an engineering club at my high school. Our group has decided to
take an in-depth look at fuel cells, and I am trying to gather background knowledge on some of the many subsets of this huge topic. We will be
working directly with the University of Utah, under a $5 million dollar grant from the National Science Foundation, that they received towards
advancing engineering, with an emphasis on environmental improvement. This summer, our group will be giving a presentation and demo to several other
high school groups at a summit held at the University. We hope to have a working fuel cell system to demonstrate at that time, and though it may not
be efficient, or novel in any way, I feel that this is a very feasible goal given the resources that the University it capable of providing.
I am sorry if I had posted my questions in haste, and hope that you and others will still be willing to help as I progress and have a more concrete
objective.
Thanks,
Michael
Sauron - 12-1-2009 at 00:29
No problem.
Google "calcium borohydride hydrogen storage"
This work is well underway and advanced and seems to be very promising for portable and reversible H2 storage.
I do not know why magnesium borohydride is not in contention. Beryllium borohydride is liquid, volatile and toxic, as is aluminum borohydride (at
least the volatile liquid aspect.) Aluminum borohydride is used to make the heavy metal borohydrides such as those of uranium and zinc.