What is silanol and what could it be used for?

**Q_Goest** · Jan24-06, 12:14 PM

Interesting advancement in the creation of hydrogen from water. What is silanol and what are the uses?

Abu-Omar's team took a compound based on rhenium, a comparatively rare metal often obtained while mining copper, and added it to the organosilane in the presence of water. Over the course of an hour, the organosilane changed completely into silanol, leaving the water and rhenium catalyst unchanged. But the team also noticed there was a gas bubbling from the mixture.

"It turned out to be pure hydrogen," Abu-Omar said. "The reaction is not only efficient at creating silanol, but it also generates hydrogen at a high rate in proportion to the amount of water."

The team estimates that about 7 gallons each of water and organosilane could combine to produce 6 1/2 pounds of hydrogen, which could power a car for approximately 240 miles.

"The big question is, of course, whether it would be economically viable to create organosilane fuels in the quantities necessary to power a world full of cars," Abu-Omar said. "As of right now, there simply isn't enough demand to make more than small volumes of this liquid, and while it's a relatively easy process, it's not dirt cheap either."

But, Abu-Omar speculated, producing organosilanes in larger quantities would bring the price down, and the byproduct – silanol – also could be recycled or sold to lessen the overall cost.

"On today's chemical market, silanol is even more expensive than organosilanes are, but their value would of course decline as well if there were suddenly millions of gallons of them on the market," he said. "These are the sorts of questions that economists would have to look at, and we have other questions of our own, such as whether these reactions can be carried out on naturally occurring hydrogen sources."

Read it here:
http://pda.physorg.com/lofi-news-hyd...said_6137.html
and here:
http://news.uns.purdue.edu/UNS/html4....hydrogen.html

Jan24-06, 01:03 PM

Isn't H2 used to synthesize the organosilanes in the first place?

**Q_Goest** · Jan24-06, 02:34 PM

No idea, rach'. Fill me in, I'm not a chemist. I'm interested in the hydrogen so if it takes hydrogen to make this stuff, it seems a whole lot less interesting.

**ShawnD** · Jan24-06, 06:46 PM

Silane is like methane, but it has silicon instead of carbon.
Silanol is silicon alcohols like Si-OH

As rach said, you need hydrogen to make silane.
http://en.wikipedia.org/wiki/Silane

Jan24-06, 07:38 PM

Edit: I'm wrong!

I think excesss hydrogen is in fact produced:
................
SiH4 + 3H20 -->SiH(OH)3 + 3H2

With an extra mole of H2 for each mole of SiH4 (comes from the H2O).

edit #2: egregious typo

Jan24-06, 07:48 PM

Link to the abstract & paper (J. Am. Chem. Soc.):
http://pubs.acs.org/cgi-bin/sample.c...ja053860u.html

Interesting read (for those who have access). In principle you can recycle part of the H2 to regenerate the organosilane, and you'd only consume water.

**Q_Goest** · Jan24-06, 08:42 PM

I think excesss hydrogen is in fact produced:
................
SiH2 + 3H20 -->SiH(OH)3 + 3H2

Rach, would this reaction be
SiH2 + 3H20 -->SiH(OH)3 + 2H2
? ? ?

I assume this is in the presence of the catalyst rhenium, is that correct?

The reaction he gives in equation 1 also gives a R subscript 4-x. What does that mean?

Is SiH2 silane? Abu-Omar talks about organosilane, is there any difference?

It sounds as if he's proposing a storage method as opposed to a source of hydrogen which is where I must have gotten confused. From the article Rash' posted:

Interest in hydrogen utilization as a fuel has intensified recently because its use in fuel cells affords water and heat as the only byproducts, and the prospects of a future hydrogen economy.1 The two key areas in need of research development are related to hydrogen sources and storage.1 While the source of hydrogen constitutes a significant scientific challenge, addressing issues of hydrogen storage, transport, and delivery is equally important. None of the current hydrogen storage options, liquefied or high-pressure H2 gas, metal hydrides, etc., satisfy criteria of size, cost, kinetics, and safety for use in transportation.

Some of the other articles I've read discuss this method of hydrogen generation on par with electrolyzing water and reforming methane to produce hydrogen, but those reactions are intended to produce hydrogen, not as a storage means. Regardless, it sounds as if he's proposing a method of storing 6% by weight hydrogen under ambient temperature and pressure which is extremely interesting to the hydrogen economy. That's about the break point we're looking for.

If SiH2 is silane though, that could be particularly nasty since it ignites in the presence of air.

**ShawnD** · Jan24-06, 08:59 PM

Originally Posted by rachmaninoff

I think excesss hydrogen is in fact produced:
................
SiH2 + 3H20 -->SiH(OH)3 + 3H2

The problem is that silane is SiH4, not SiH2. All 4 of those hydrogens come from HCl, which is made from Cl2 and H2.

What must be remembered is that you can't get something for nothing. If it seems like the extra hydrogen is a net gain coming from water, it's because your starting materials (Si, H2, and Cl2) were made using a lot of energy, and all of that energy eventually traces back to power made using conventional means (oil, nuclear, wind, whatever). If this idea is being pitched as another free energy type idea, it's not impressive by a long shot. If it's an energy storage idea, it's basically just another design for a fuel cell, aka batteries.

Jan24-06, 11:46 PM

Originally Posted by ShawnD

The problem is that silane is SiH4, not SiH2. All 4 of those hydrogens come from HCl, which is made from Cl2 and H2. .

Sorry about that... fell asleep at the keyboard or something.

Jan24-06, 11:52 PM

Originally Posted by ShawnD

What must be remembered is that you can't get something for nothing. If it seems like the extra hydrogen is a net gain coming from water, it's because your starting materials (Si, H2, and Cl2) were made using a lot of energy, and all of that energy eventually traces back to power made using conventional means (oil, nuclear, wind, whatever). If this idea is being pitched as another free energy type idea, it's not impressive by a long shot. If it's an energy storage idea, it's basically just another design for a fuel cell, aka batteries.

It's none of these. It merely demonstrates a particular catalytic method to get hydrogen from water; it doesn't much of a purpose, that's why I've been using the word "hype" so much. Especially when the author gets really speculative and suggests catalysts could liberate H2 from hydrocarbons in landfills.

Q - organosilanes are in general compounds with both C-H bonds and Si-H bonds, such as (CH3)3SiH.

**Q_Goest** · Jan25-06, 11:44 AM

Thanks for the feedback Rach and Shawn.

Also, thanks for clarifying the reaction, Rach.

Wow, I can't believe he's suggesting using silane as a reactant. Way too dangerous for practical purposes on fuel cell vehicles. The company I work for installed a silane distribution hub about 6 or 8 years ago and I remember hearing that even the tiniest leaks from such things as cylinder valves instantly ignited. Not good...

Do you think there is any way of getting around the issue of using silane or other dangerous gasses? Do the byproducts of the reaction present any safety hazard?