hi
hopefully someone with more brains than me can answer this question more scientifically.
basically i have built a rector that uses aluminium powder, sodium hydroxide and water to produce vast amounts of hydrogen.
now heres the problem, i am told that unless the aluminium and sodium hydroxide are mixed in the correct proportions there are a few problems.
1: far too much heat is produced.
2: aluminium salts are produced (not sure which)
3: the geatinous aluminium hydroxide that should be produced is redisolved by excess sodium hydroxide (too many reactions for my liking)
now then for the question,
can anyone use the chemical formula for this reaction to determine what amounts of aluminium and sodium hydroxide should be mixed. im guessing you can add as much water as you like...???
also i have always wondered, if you mix aluminium with sodium hydroxide you get aluminium hydroxide, where does the sodium go??? the chemical formula iirc shows the sodium bonded with the aluminium hydroxide but its not mentioned in the name (so to speak)
any help would be great guys
G'day Hydro-Cell,
Send a personal message to Dave ( ResinRat2 ), He is our resident research chemist. He will explain the chemical reaction to you.
Hans von Lieven
If you got this working how long would it take before aluminum got too scarce and expensive to use.
DAVE
A lot of towns in the USA have started land filling recyclables [no longer cost effective]
Chet
nothing will happen in this mixture at all.Sodium is more rective than aluminium and won't give out OH to it.
uppps,i was wrong to some extent :) there will happen some things but i was correct that Na won't give its OH group away :)
ok i took my dust chemistry book from the shelf..
NaOH will uncover the Al surface so it can react with water:
1) Al2O3+2NaOH+3H2O====>2Na[Al(OH)4] (salt solvable in water)
Water reacting with Al:
2) 2Al+6H2O===>2Al(OH)3+3H2
as next step Al(OH)3 is further bond into salt:
3) Al(OH)3+NaOH===>Na[Al(OH)4]
The thing to accent is than Al is always covered by its oxide,so if u have Al powder it is in fact Al surrounded by Al2O3.
So in first step NaOH solves the Al2O3,then Al under it reacts with water to produce Al(OH)3.The latest one gets again turned into salt by NaOH.
The finer the powder the more NaOH will go to eat the Al2O3.So this part of the reaction depends on the surface area and the tickness of the Al2O2.If we consider this powder as sphere-like formation,the Al wil make most of its mass,so i would negate the first reaction needs.U can also take the experimental value like +5% of what u need for reaction 3 to be completed.
Without the first reaction in the consideration,for ideal reaction u need for every 54 gram of Al ,80g of NaOH.
In first reaction for every 102g of Al2O3 u need 80g of NaOH.
;D i see resinrat was faster by 2 minutes :)
http://www2.uni-siegen.de/~pci/versuche/english/v44-10.html
You will get a gooey mess.
So what was the question?
Quote from: ramset on January 19, 2009, 06:31:57 PM
DAVE
A lot of towns in the USA have started land filling recyclables [no longer cost effective]
Chet
That is interesting. Where I live they still collect them.
Actually, this reaction can be controlled somewhat. Don't worry about the ratios of the reactants. What you want is to CONTROL the reaction rate and one way to do this is to add one component into the other in a controlled manner.
You can have one container that holds the aluminum and slowly drip the NaOH solution into it. This would control the heat and gas rate off: or you could hold the NaOH solution in one container and slowly add the aluminum powder into it. Stopping the addition would allow the reaction to peter out and stop at that point,.
Just an observation on ways to possibly control the reaction rate. You won't be able to INSTANTLY stop the reaction, but you can allow it to slow and stop in a controlled manner.
G'day Dave
Isn't this similar to making acetylene gas with calcium carbide. They used to dribble water on the calcium carbide in measured quantities to generate the required amount of gas. You also wind up with a gooey mess in the container after a while. ;D ;D
Hans von Lieven
Hi Hans, I used to go Spelunking in my younger days and there were people that swore by the carbide lamp over the battery lamp. You are right though, you would end up with a mess at the end that had to be disposed of.
The same with this idea.
I actually did a long series of experiments trying to get this reaction with the aluminum and sodium hydroxide under control. I was using the theory that the aluminum could be regenerated at the same time the hydrogen was being produced. I always came close to controlling the regeneration, but no matter how carefully I regulated the regeneration voltage, the aluminum was always either consumed or plated on to the tungsten cathode.
The bad part about this aluminum-hydroxide experiment is that in the end you are left with toxic waste that can't safely be just thrown down the sink. It would need to go to a toxic landfill.
Aluminum is expensive because of the amount of energy needed to extract it from it's mineral bonding. Any gain is basically getting the energy back that was used to get it into it's elemental form. You can burn limestone but that isn't very friendly.
hi guys and thank you for your responses
just to clear a few things up.
ok here goes.
the control method is sorted, i am able to distribute aluminium powder in 10gram doses at anytime i want to administer it.
the messy goo, is under control, the leftovers are collected in a cell that when full and removed from the reactor will close itself. it cannot be opened unless in the reactor!!
the Hydrogen released is 99% pure, during the opereation of the reactor it allows small amounts of air into the stream, this was an oversight on my part and is being worked out.
the waste leftover will be sent to companies or factories where it can be converted back to aluminium, i have read that the leftover product is aluminium sulphate (correct if wrong)
i have also read that aluminium sulphate is 1 step away from being aluminium as far as reactions go, by electrolysing the aluminium sulphate i belive it will convert back to aluminium (not sure on this, only scratched the surface)
i have access to machinery etc to turn scrap aluminium into aluminium powder/pellets. at the current price of scrap it is costing me about 80p per kg. at this price of aluminium the reactor can provide approx 1200 litres of hydrogen for 80p. even when the price of scrap was £1.30 per kg it would only cost approx £2.50 per kg.
in terms of running a small engine (just a for instance) 1200 litres of hydrogen will supply a 200cc engine for 4 hours. it will also consume 3 litres of petrol.
on this basis at present the aluminium is 1/3 the cost of petrol, when the price of scrap goes up it will pretty much break even on current cost of petrol. but as always petrol will also rise in price.
due to aluminium being recyclable in theory we should never be able to run out of fuel.
the reactor can hold upto 10kg providing potentially 12000litres of hydrogen, or run a smart car for approx 12 hours potentially 750 miles on £15
the reactor will be fitted to either a fuel cell (very expensive) or a free piston engine (cost effective) free piston engines are about 50% efficient and can be designed to run on hydrogen, output is electricity only.
please feel free to give input
Hi Hydro-cell,
The leftover waste product will be aluminum-hydroxide with sodium salts in the water solution. The sodium will be attracted to the aluminum hydroxide and form sodium aluminum hydroxide. I am not sure where you got the aluminum sulfate information. It might be for a different reaction, maybe a sulfuric acid solution used to make a hydrogen cell with, but there is no sulfer in your reaction.
The waste can probably be treated with an acid wash and the aluminum precipitated out. I haven't looked it up but it can probably be done in this way. I am sure if you tell the reclaiming company what was done that they would know the procedure to reclaim the aluminum.
Good luck,
Dave (RR2)
hi resinrat2
cheers for the info, i got mixed up with the aluminium sulphete. got too many experiments going on.
i was reading a paper on NaOH safety, it says coming into contact with aluminium, zinc, or tin will release hydrogen.
is it likely that tin will allow the production of more hydrogen??? as it is cheaper its just a thought.
was thinking of maybe a mixture of tin and aluminium or something.
if you can put a reaction here... aswell as the hydrogen yeilded from 1kg of tin i would be very gratefull.
i also found out that the sodium aluminium hydroxide is known as sodium tetrahydroxoaluminate.. however there is very little information on this. can anyone shed a little light on this???
need to know if it is toxic, harmful, burns skin etc.
please dont give answers that you "think" may apply, im looking for solid answers, a datasheet would be good or some form of coshh sheet.
cheers
chris
Once the process is completed simply turn the Alumina back to the manufactures. For all that you turn in that will be the amount that does not have to be mined . And mining is the most costly part of their process. Recycle
I have read that when you use this process that you get out 100% of the energy that was put into the manufacturing process not counting the mining and if you recycle there is no mining for that quantity .
It's not the mining costs as much as the energy needed to extract the aluminum from it's ground state mineral bonding. They use naoh in this process and electrolysis to precipitate the aluminum. Would make a nice battery though especially if you use high voltage lowamp electrolysis to precipitate the aluminum.
Your going head to head with lithium technologies and other battery systems so it may be a difficult road.
Greetings:
Project sounds fascinating.
I wanted to ask you, when you said "the waste leftover will be sent to companies or factories where it can be converted back to aluminium", do you know of any firms that currently do this?
I have a LARGE amount of aluminium hydroxide (inert) that needs to be recycled/reused.
Please forward me any information you may have on this process, how how *energy intense* it may be?
Thanks in advance :)
Quote from: Hydro-Cell on January 19, 2009, 03:58:35 PM
snip...
basically i have built a rector that uses aluminium powder, sodium hydroxide and water to produce vast amounts of hydrogen.
snip...
Try this experiment. Fill a container to 3/4 full with water / NaOH, then insert an aluminium and copper rod into the solution about a 1 cm apart, with the top of the rods a few centimeters above the level of solution. Then observe.
The aluminium will, on contact with the solution, begin to produce hydrogen. The copper rod will not.
There will be a potential difference between the copper and aluminium facilitated by the hydroxide solution.
Place a wire connector to the tops of the two rods to short their potential out. The copper rod will then produce oxygen, and the aluminium rod will produce even more hydrogen.
Be careful! Oxygen and Hydrogen re-combine very easily when extracted together into the same storage container.