aliced25
Hazard to Others
Posts: 262
Registered: 31-7-2010
Member Is Offline
Mood: No Mood
|
|
High-Pressure Hydrogen (10MPa)
Yeah, if you are anything like me you've seen all the cool hydrogenations using 100 atm of hydrogen (1atm is about 100kpa, 100 atm = ~10MPa) and
thought bugger, as if it were possible to pressurise hydrogen to that level in the home lab.
Fear not, I found an interesting article, in a Japanese article:
-------------------------------------------------------------------------------
Hydrogen Production from Waste Aluminium at Different Temperatures with LCA
Takehito Hiraki, Masato Takeuchi, Masaaki Hisa & Tomohiro Akiyama
Materials Transactions
Vol.46(5) 2005, pp.1052-1057
http://www.jim.or.jp/journal/e/46/05/1052.html
Abstract
The recycling of waste metallic aluminum with high chemical exergy, which consumes a large quantity of electricity in the refining process, is
insufficient. In particular, the so-called dross generated during the remelting process a part of recycling requires expensive treatment, particularly
when the metallic concentration is less than 20%, before it can be landfilled. The purpose of this study is to produce hydrogen from waste aluminum
sources, such as dross, using an aqueous solution of sodium hydroxide in a beaker and an autoclave. During the study, the effects of temperature of
the aqueous solution on the rate of hydrogen generation are to be chiefly examined. The result obtained from an XRD analysis showed that the white
product that precipitated during the experiments contained aluminum hydroxide, the rate of hydrogen generation significantly increased with the
concentration of sodium hydroxide and temperature of the aqueous solution, and the activation energy was 68.4 kJ mol1. In the autoclave experiments,
hydrogen is released quickly, along with an increase in the inner pressure to a minimum of 1.0 MPa and an increase in the temperature above 473 K. The
results suggested a possibility of a new cost effective process of hydrogen production from waste aluminum along with the by prodution of sodium
hydroxide. The life cycle assessment (LCA) of the proposed process for producing not only 1 kg of hydrogen but also 26 kg aluminum hydroxide from
waste aluminum was carried out to assess the energy requirement and amount of carbon dioxide emissions. Results suggest that the energy requirement of
our process is only 2% and the amount of carbon dioxide emissions is 4%, in comparison to a conventional method.
-------------------------------------------------------------------
Now, I'm thinking the addition of a strong solution of NaOH to Al powder in a pressure vessel, with regulation of addition equipped with valve (and
relief valve) and we'd have our very own High-Pressure Hydrogen Generator for all those previously inaccessible hydrogenations. It should be possible
to control the pressure (after all, with temperature control they kept it to 1.0MPa (or 10atm), so this looks like a useful find.
Keep it mind it is kind of flammable and explosive, but with people making home-made RDX and shit, Hydrogen looks almost tame.
Attachment: Hiraki.etal.Hydrogen.Production.from.Waste.Aluminium.at.Different.Temperatures.with.LCA.pdf (188kB)
This file has been downloaded 469 times
[Edited on 12-5-2013 by aliced25]
From a Knight of the Realm: "Animated movies are not just for kids, they're also for adults who do a lot of drugs." Sir Paul McCartney
|
|
|
Adas
National Hazard
Posts: 711
Registered: 21-9-2011
Location: Slovakia
Member Is Offline
Mood: Sensitive to shock and friction
|
|
The hydrogen generated this was contains water, NaOH and aluminium hydroxide. This can easily destroy many hydrogenations.
Never try this with Al powder unless you want to blow yourself up. Reaction with compressed Al foil is much better and more controlled.
Rest In Pieces!
|
|
|
aliced25
Hazard to Others
Posts: 262
Registered: 31-7-2010
Member Is Offline
Mood: No Mood
|
|
Yet it is claimed as being 99.99% pure? Run it through a drying column on the way to the pressure vessel, that would physically block any contaminants
except water and absorb the latter.
From a Knight of the Realm: "Animated movies are not just for kids, they're also for adults who do a lot of drugs." Sir Paul McCartney
|
|
|
Adas
National Hazard
Posts: 711
Registered: 21-9-2011
Location: Slovakia
Member Is Offline
Mood: Sensitive to shock and friction
|
|
Quote: Originally posted by aliced25  | | Yet it is claimed as being 99.99% pure? Run it through a drying column on the way to the pressure vessel, that would physically block any contaminants
except water and absorb the latter. |
If you can purify it, then OK. No problem with this.
Rest In Pieces!
|
|
|
solo
International Hazard
Posts: 3975
Registered: 9-12-2002
Location: Estados Unidos de La Republica Mexicana
Member Is Offline
Mood: ....getting old and drowning in a sea of knowledge
|
|
"The hydrogen generated this was contains water, NaOH and aluminium hydroxide. This can easily destroy many hydrogenations."
.......I've done my share of hydrogenations for ten years, and never had problems with hydrogenations that contained water.....solo
It's better to die on your feet, than live on your knees....Emiliano Zapata.
|
|
|
Adas
National Hazard
Posts: 711
Registered: 21-9-2011
Location: Slovakia
Member Is Offline
Mood: Sensitive to shock and friction
|
|
| Quote: Originally posted by solo | "The hydrogen generated this was contains water, NaOH and aluminium hydroxide. This can easily destroy many hydrogenations."
.......I've done my share of hydrogenations for ten years, and never had problems with hydrogenations that contained water.....solo
|
It is not just about the water... And the NaOH and Al(OH)3 can make your product impure, which you probably don't want.
Rest In Pieces!
|
|
|
S.C. Wack
bibliomaster
Posts: 2419
Registered: 7-5-2004
Location: Cornworld, Central USA
Member Is Offline
Mood: Enhanced
|
|
He isn't trying to start an argument with you, he's telling about his hydrogenation experience with water...so...does high pressure stop foaming at
all?
|
|
|
zed
International Hazard
Posts: 2284
Registered: 6-9-2008
Location: Great State of Jefferson, City of Portland
Member Is Offline
Mood: Semi-repentant Sith Lord
|
|
Depends on what you wish to hydrogenate. For the reduction an imine, the presence of a little water generally does no harm.
If however, you wish to produce NaAlH4, via the high pressure hydrogenation of metallic Na and powdered AL, in toluene.......H2O is a no-no.
|
|
|
aliced25
Hazard to Others
Posts: 262
Registered: 31-7-2010
Member Is Offline
Mood: No Mood
|
|
And yet a drying tube is going to stop any of the above getting into the reaction ain't it? Either mechanically or via absorption
From a Knight of the Realm: "Animated movies are not just for kids, they're also for adults who do a lot of drugs." Sir Paul McCartney
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
