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Endimion17
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Well if the moment has not passed, then it's ok, I guess. 
I wrote:
"The moment I've read "onboard electrolysis" I knew this is doomed. It's the basic flaw I saw... around twenty times so far, on various places online.
Electrolysis consumes more energy than its products can yield when they recombine. That is the law and nobody can break it because that's how nature
works.
Inserting electrolytical cell in the car is in fact widening the chain of energy transformations and thus creates more opportunity for wasting it.
This is a huge waste of energy because electrolysis of water is a very consuming process.
If you're extracting energy from the gasoline+oxygen reaction in your car, you might as well use it directly to power your wheels and electric
components. Why inserting anything more? To waste more gasoline? Because it will be wasted.
The only idea that could be feasible is the idea that hydrogen and oxygen might increase the efficiency of burning gasoline, but not only that doesn't
happen (and yes, commercial exhaust gas detectors tend to derp and give false readings when people try that), but it would have to be a huge
improvement of the efficiency to cover up for the huge waste in the first place.
Basically, when you strip this idea naked, you get a water fueled car, a known hoax. No amount of decorative bits can save it. It's
wrong in its essence."
It's nothing I haven't said before. I'm actually surprised by the will of some people to go so far with these things, but in the same time ignore the
basics.
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deltaH
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Ammonia electrolysis
Firstly, before I commence with this new thread, let me state for the record that I was very sad to see that my previous thread for the generation of
hydrogen from glycerine electrolysis to power fuel cells shut down because moderators seem to believe I was proposing pseudo science... I'm going to
resist the urge to lash out at them
Instead and in defense, I will now go down a more rigorous scientific approach and start with known science and work my way up back to where we
previously left off and hopefully the powers that be will realize their error and merge the threads and reopen the previous one.
I'll start with research into the electrolysis of ammonia to generate hydrogen.
There is a ton of literature on this, but one research group specifically has done excellent work on the topic, namely Dr Botte of Ohio university, so
for brevity I will refer readers to their site for their literature needs on this topic:
See http://www.ohio.edu/ceer/research/ammonia.cfm
Incidentally, it was their work that got me thinking about the topic in the first place.
Basically, the idea is quite simple. You electrolyse a solution of ammonia in strongly basic media. At the anode you oxidise the ammonia to form
nitrogen gas, at the cathode you reduce water to form hydrogen. The half reactions are:
2NH3 + 6OH- -------> N2 + 6H2O + 6e-
2H2O + 2e- -------> H2 + 6OH-
The balanced net reaction is quite simple 2NH3 => N2 + 3H2
The theoretical standard potential of this process is 0.058V... practically very close to 0V (this is quoted from them, so don't argue with me about
it).
In reality, you have a whole bunch of overpotentials creeping in that makes this far less efficient. The main challenge comes in reducing the
activation energy overpotential at the anode, which is just a fancy way of saying you need a catalyst there to help ammonia dissociate into nitrogen
and hydrogen, particularly when you are running this process at high rates. That way you don't end up wasting too much energy by heat production and
you can come as close as possible to the minimum thermodynamic energy requirement for such a process of 1.55 W-h per gram of H2 produced (I assume
they are referring to a minimum on their website where I get this number from).
This might seem quite good, it isn't really, why? Because ammonia isn't a particularly good fuel on energy density arguments compared to organic
molecules. But it does have the up side of running very cleanly, producing only nitrogen gas as the co-product, i.e. no CO2 as the electrolytic
oxidation of an organic molecule might.
But what people forget is where does the ammonia come from?
The best you can do is use the Haber process and surprise surprise, that needs hydrogen!
Unfortunately, most ammonia plants today use hydrogen derived from either coal gasification or steam reforming (fossil fuel hydrogen sources... not
sustainable!). However, there's off course nothing preventing one from deriving it from more sustainable resources such as biomass gasification or
steam reforming of natural gas derived from sewerage or biomass.
Anyhow, I trust people will agree there's no pseudo science in deriving hydrogen from ammonia by electrolysis and can accept those published numbers
for starters?
Thanks
[Edited on 3-10-2013 by deltaH]
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woelen
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Ammonia resists oxidation amazingly well. I once was curious about what would happen if I electrolyse ammonia with some NaOH to make the solution
conductive. The result is simple: hydrogen at the cathode, oxygen at the anode in a 2 : 1 volume ratio (the mix made a nice detonating gas). The
ammonia was not (or hardly not) oxidized. I also needed severals volts before a decent current flowed through the cell. I used a metal cathode and a
graphite anode.
Of course, this is not a proof of you being completely wrong, but it at least gives evidence that it is not easy at all to reduce the required
potential to perform some electrolysis. Some compounds require a lot of activation energy to have them reacted and in the case of electrolysis this
means that you lose a lot of energy in the form of heat.
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deltaH
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Hi Woelen,
Thank you for your civility. Yes the point is that graphite has the maximum overpotential possible and is probably completely electrocatalytically
inactive for this system. The nitrogen hydrogen covalent bond is very hard to break without the right catalyst.
In fact, to emphasise this point, consider the reverse process, making ammonia from nitrogen and hydrogen is also extremely hard to accomplish without
a catalyst!
While the researchers of Dr Botte's team propose their own electrocatalysts for this system, I would hazard that a simple platinum plated anode should
give reasonable results at low current density, as platinum is very active for ammonia dissociation.
However, again let me emphasise that a simple platinum plated anode would only work well at low current because the surface area of a simple platinum
coating is not high. If you want to operate at very high rates and current, you need to disperse the platinum on the anode, or even better and go the
whole nine yards with the anodes proposed by the researches at Ohio.
[Edited on 3-10-2013 by deltaH]
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deltaH
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I think this brings us to an interesting junction that would bear merit to discuss. The propensity to get confused between thermodynamic arguments and
chemical kinetic arguments.
Let consider two systems for example:
1. Water electrolysis under alkaline conditions.
2. Ammonia electrolysis under alkaline conditions.
This systems are similar on face value, but the standard cell potential for the water electrolysis is much higher than the ammonia one, compare for
case 1: Ecell std. = -1.2V and for case 2: Ecell std. = 0.058V from the Ohio university website.
This means that it is thermodynamically much easier to electrolyse ammonia than water.
Now comes in the second part of to any chemistry story, chemical kinetics!
The nitrogen hydrogen bond needs to be dissociated in any mechanism that would oxidise ammonia on the surface of an anode. This would occur as a
series of what in chemical kinetics is called elementary reaction steps.
for example, starting with NH3 => NH2* + H*
the star's simply denoting that this is a surface adsorbed species on the anode, not some radical, but bonded to the surface, usually as a surface
hydride specie if a metal anode is used, for example.
After this point a whole bunch of things can happen but the point is it goes via simple steps that have an activation energy barrier to overcome.
The larger the activation energy barrier (the poorer you electrocatalyst) the larger the overpotential becomes and the lower you efficiency of
electrolysis. There are other mechanism that lead to yet other types of overpotentials, but the activation energy overpotential is usually the most
serious one that needs to be addressed when starting out.
Now back to the case of ammonia, since catalysts cannot alter chemical thermodynamics, only chemical kinetics, something that is catalytically a good
catalyst for the forward reaction is by definition also a good catalyst for the reverse. So since we all know that platinum is a very active catalyst
for the ammonia synthesis in the Haber process, it should work just as well in catalysing the split of ammonia into hydrogen and nitrogen by
electrolysis, albeit it would be expensive!
Incidentally, I was told by the person who taught me catalysis that Haber, understanding this principle, screened materials as potential catalyst for
his process not by trying to make ammonia with them (which required very high pressure), but in fact simply by trying to decompose ammonia back to
nitrogen and hydrogen by applying heat at ambient pressures (much easier to carry out experimentally). He found that platinum was most active in
ammonia decomposition, so therefor was also a good catalyst when he shifted conditions to favour a ammonia product in the chemical equilibrium by
applying very high pressures.
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Bezaleel
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And do you have the list of catalysts haber tried before deciding for platinum? Maybe lead dioxide might be a cadidate as well. If it is only a little
less effective, you might be a whole lot cheaper off.
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deltaH
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Hi Bezaleel,
I'm afraid I do have a list of what else Haber considered, though I know that modern ammonia synthesis catalysts use promoted iron. That said, I
believe that ruthenium is king... a metal close to my heart as I worked on ruthenium catalysts during my PhD research.
I also know that pool chlorinator anodes are [usually] made of a ruthenium MMO coated titanium as this has the lowest activation over potentials for
chlorine oxidation. So if one wants to experiment with ammonia electrolysis at home, maybe this is the way to go... sure beats having to work with
platinum!
I don't know how stable the RuO2 on those chlorinator MMO electrodes may be in a caustic environment, I would suspect there is a very high chance that
it would be oxidised to ruthenates and leach off.
So your choices are platinum (difficult but maybe best?) or RuO2 MMO from a pool chlorinator, easier but will probably leach out?
Talk about being between a rock and a hard place!
[Edited on 3-10-2013 by deltaH]
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deltaH
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Ha ha, just took a look at those Ohio guys' catalyst, turns out it is a tri-alloy of platinum, ruthenium and nickel...
No surprises there
Here's the link for lazy people like me:
https://www.google.com/patents/US7485211?dq=7485211&hl=e...
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kmno4
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I do not understand - what do you want to discuss about ?
Did you bother to read (at least) literature (by Dr.Bottle) cited on your first post (ohio.edu link) ?
Слава Україні !
Героям слава !
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Varmint
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The fact that hydrogen is needed to create ammonia is the singular most important thing to embrace.
The OP states hydrogen is currently derived from non-renewable energy sources is a point of interest certainly, but then goes on to assume it could be
obtained using other methods. Either way, you start with hydrogen.
Frankly, all discussion should stop right there. If you have hydrogen, there is no real value in using it to create ammonia, only to disassociate
that ammonia at a later time to recover the target hydrogen.
There might be some arguement that could be formed over safe storage or transportation where ammonia seems like a suitable "container" for hydrogen,
but the bottom line is ANY process past the point of having hydrogen available to create ammonia begins a chain of losses.
Instead of hydrogen, the key thing to be researched is virgin sources of ammonia.
If you can't find a means of collecting or synthesizing raw stock ammonia, then no matter how efficient you can make the ammonia --> hydrogen
process you are operating under the substantial losses required to create ammonia from HYDROGEN SOURCES.
The key is energy efficiency, start to finish. If you create an advanced fuel pellet that outgasses virtually unlimited supplies of hydrogen on
demand, but it takes all of the available output from a typical nuclear electricity generating station for a year to create one pellet, you have
created a scientific curiousity that has no practical application.
I suspect the original post was deleted for good reason, there is no compelling reason to discuss hydrogen synthesis from ammonia, when ammonia itself
requires hydrogen for its synthesis.
Why is this not obvious?
DAS
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deltaH
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Hi Varmint
Thanks for your raising your points in a civil manner, though I beg to differ/expand thus:
| Quote: | | Frankly, all discussion should stop right there. If you have hydrogen, there is no real value in using it to create ammonia, only to disassociate that
ammonia at a later time to recover the target hydrogen. |
I also hold that ammonia isn't that great for this purpose, I proposed using glycerine in the thread that was closed because you can [indirectly]
'grow' glycerine, you can't 'grow' ammonia. My point here is that this isn't pseudoscience, you CAN generate hydrogen from fuels fairly easily by
electrolysis and I was simply referencing the well researched topic of ammonia electrolysis as a case study.
However, that said, there is a BIG necessity to generate hydrogen for fuel cells on board, its an active topic of research for many scientists and
inventors such as myself. This because you can only 'tank up' with comparatively little hydrogen in a car with existing technologies.
| Quote: | | Frankly, all discussion should stop right there. If you have hydrogen, there is no real value in using it to create ammonia, only to disassociate that
ammonia at a later time to recover the target hydrogen. |
In the chemical industry, converting a low density gas into something more dense for the sake of transport is routine! This is usually done by
liquefaction, but liquefaction isn't very practical in the case of hydrogen, nor would you achieve nearly the same energy density as hydrocarbon fuels
would even if you did.
| Quote: | | There might be some arguement that could be formed over safe storage or transportation where ammonia seems like a suitable "container" for hydrogen,
but the bottom line is ANY process past the point of having hydrogen available to create ammonia begins a chain of losses. |
Indeed, which is why I proposed glycerine in the first place on the thread that was closed.
| Quote: | | I suspect the original post was deleted for good reason, there is no compelling reason to discuss hydrogen synthesis from ammonia, when ammonia itself
requires hydrogen for its synthesis. |
It hasn't been deleted, it's been locked, so you're free to read it. I would suggest you read it before passing judgement. The post is called
'Hydrogen from [bio]glycerine by electrolysis for fuel cells' and it's just below this one in this forum.
Hope that clarifies why this is not obvious and thanks for reasoning and not just making inflammatory remarks.
Believe me I appreciate it!
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Varmint
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OK, I took a look at the other thread...
In situ electrolysis for automobiles?
Wow.
Interesting to note how you point out industry commonly uses liquifaction for transport, then go on to say it wouldn't really work here. Well, I
already implied it wouldn't work here, I was giving you the opportunity to make a compelling case for the wasted energy for going from hydrogen
---> ammonia ---> hydrogen. Transport was a bone you could have picked up and run with, instead you chose to "educate" me.
In the other thread you discuss glycerin + H2O2 as a holy grail, but when challenged on making the combination conductive you easily flit off to
discuss formic acid as an example of a conductive electrolyte, then you explain why formic acid presents problems. OK, now that we're back at
glycerin/peroxide, where soes the conductivity to support electroyis come for?
Suddely the vision changes to having sulfuric acid as the electrolyte/catalyst, adding the "fuel" to be electrolysed "drop wise".
Aside from the obvious, it pays to consider the energy required to propel a vehicle down the road. 100HP = 74,5699 watts.
That's a lot of drops. That's a huge reaction, generating lots of heat which must be carried away, and presumably lots of H and O to combust. I
can't begin to envision a reaction system capable of generating 10's or 100's of thousands of kilowatts that could handle being operated for minutes,
let alone hours.
DAS
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deltaH
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Hi Varmint
| Quote: | | ...instead you chose to "educate" me |
My goodness, not at all, simple discussing.
| Quote: | | glycerin + H2O2 as a holy grail |
Note at all, just a idea to be investigated / debated, instead most people just lobbed profanities, I try to engage with those who make / raise
points, such as yourself
| Quote: | | but when challenged on making the combination conductive you easily flit off to discuss formic acid as an example of a conductive electrolyte, then
you explain why formic acid presents problems. |
No the formic acid post was an example to show (using data easily available on wiki's standard electrode potential table) how dE for the electrolysis
of functionilised organic molecules is not that bad.
About the sulfuric acid, the thread was closed before I could respond (next day here in SA)
I def want to discuss that because it's a valid point, but I want to wait for the post to be reopened, this one is about ammonia electrolysis.
| Quote: | | Suddely the vision changes to having sulfuric acid as the electrolyte/catalyst, adding the "fuel" to be electrolysed "drop wise".
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No that was always my vision, see the full details of that idea on my website as reference in that thread. It's just we got to the stage of starting
to discuss that, then I got cut off.
As for the drop wise, that is only for test purposes and small scale operation, but again this discussion belongs there, not here.
| Quote: | | That's a huge reaction, generating lots of heat which must be carried away, and presumably lots of H and O to combust. I can't begin to envision a
reaction system capable of generating 10's or 100's of thousands of kilowatts that could handle being operated for minutes, let alone hours.
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Not so sure what you mean here, please clarify.
Sorry have to run now... but will respond later. Apologies!
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Traveller
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The scary thing is, someone will probably be foolish enough to give him a few million dollars in taxpayer money to continue his research.
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Fantasma4500
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Quote: Originally posted by woelen  | | The result is simple: hydrogen at the cathode, oxygen at the anode in a 2 : 1 volume ratio (the mix made a nice detonating gas).
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not trying to be too offtopic.. woelen if you ever considered it, stoichiometrical is not always the fastest of all, i recall 4000 m/s H2 + O2 in the
ratio 75 + 25 STRAIGHT UP was the absolutely best ratio they could get, peaking at 4000 m/s
also, NH3 is made by N2 + 3H2 if im not entirely wrong, i dont see how you can make NH3 with hydrogen to make hydrogen..?
for efficiency i would say simple 316 steel with NaOH (aq) in which im trying to build a decent efficiency cell for a few gigs.. (=
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deltaH
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| Quote: | | also, NH3 is made by N2 + 3H2 if im not entirely wrong, i dont see how you can make NH3 with hydrogen to make hydrogen..? |
I don't exactly understand your question, can you please rephrase it? Are you wondering why it's reversible?
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deltaH
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Sorry meant to also reply to this:
| Quote: | | for efficiency i would say simple 316 steel with NaOH (aq) in which im trying to build a decent efficiency cell for a few gigs.. (=
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If you meant for the ammonia electrolysis, I doubt very much that it would have the necessary catalytic
properties, you'd just end up with water electrolysis, but also highly inefficient at that.
You might have better luck with tracking down some special grades of titanium for the anode that contain small amounts of palladium, or ruthenium and
nickel. I don't know if the amounts of PGM in them are enough to have a noticeable effect, but at worst you will have a longer lasting anode?
From the wikipedia article on titanium alloy I quote thus:
"Grade 7 contains 0.12 to 0.25% palladium. This grade is similar to Grade 2. The small quantity of palladium added gives it enhanced crevice corrosion
resistance at low temperatures and high pH."
"Grade 11 contains 0.12 to 0.25% palladium. This grade has enhanced corrosion resistance."
"Grades 13, 14, and 15 all contain 0.5% nickel and 0.05% ruthenium."
If you track down a small sheet or tube of any of these, you might have an improved anode for electrocatalytic reasons.
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deltaH
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Out of interest, the spot price of ruthenium has dropped to some extreme lows of late, it's currently at $57/ounce. Pretty amazing as it was trading
at over $840/ounce in 2007!!! Time to get your hands on ruthenium if you can... but good luck convincing Johnson Matthey to sell it to you!
I've always believed that ruthenium is WAY under rated for it's catalytic value and considering current prices compared to other PGMs...
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blogfast25
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deltaH:
Can you answer a very simple question, please?
Is your purpose the onboard electrolysis of glycerol to CO2 and hydrogen with subsequent use of the generated hydrogen for the propulsion of the same
vehicle?
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deltaH
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| Quote: | | Is your purpose the onboard electrolysis of glycerol to CO2 and hydrogen with subsequent use of the generated hydrogen for the propulsion of the same
vehicle? |
No, my purpose is electrolysis of glycerine + H2O2 + water to CO2 and hydrogen for propulsion of
same vehicle where in a second step the hydrogen generated is oxidised to water using air in hydrogen fuel cells.
Nearly what you said, you omitted peroxide, this makes the difference between it potentially working and not. Sorry for having to say this, maybe you
are not trying to catch me out, but I have to be exact with all the flack I'm taking on this.
Big black box around whole system (electrolysis + fuel cells) and overall equation becomes:
C3H8O3 + 3O2 + H2O2 => 3CO2 + 5H2O + Energy
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deltaH
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Guys it is very late here in SA and I need to sign off and go to sleep. Please I don't want to find tomorrow when I wake up, as I did this morning,
that you post a bunch of challenge question but then close the thread without giving me a chance to respond... even worse, then accuse me the next
thread that I avoided the challenge as was also posted today. So if I don't reply in the next few hours, I am SLEEPING.
The behaviour of some regular posters here has been poor in my opinion. PLEASE challenge me on my reasoning if you want to help me with this idea. If
you don't simply don't, but all this nasty tone needs to stop (not saying you blogfast, nothing wrong with your question) and moderators please take
care of that. I am trying my best to stay neutral and deal with points raised calmly, but my calm nerves can only take me so far.
I have raised this in the proper channels as I beleive is correct (u2u), hopefully people will consider. I am not angry with anyone, just tired of
insults and want to continue doing what I love best, amateur science and innovation. Sigh.
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blogfast25
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| Quote: Originally posted by deltaH | No, my purpose is electrolysis of glycerine + H2O2 + water to CO2 and hydrogen for propulsion of same vehicle where in a second step the hydrogen
generated is oxidised to water using air in hydrogen fuel cells.
Nearly what you said, you omitted peroxide, this makes the difference between it potentially working and not. Sorry for having to say this, maybe you
are not trying to catch me out, but I have to be exact with all the flack I'm taking on this.
Big black box around whole system (electrolysis + fuel cells) and overall equation becomes:
C3H8O3 + 3O2 + H2O2 => 3CO2 + 5H2O + Energy |
I don’t think anyone here is trying to insult you. We’re deeply sceptical, as we SHOULD be.
My take on this is:
C3H8O3 + 3O2 + H2O2 + Energy1 => 3CO2 + 5H2O + Energy2
… with Energy1 > Energy2 (apart from the obvious problem of the electrolysis of glycerol to CO2 and H2)
No offense intended.
Sleep well (you’ll need it!)
[Edited on 3-10-2013 by blogfast25]
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Traveller
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Doesn't adding an oxidizer to glycerol just cause it to burn? I know this happens if you add potassium permanganate to glycerol.
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bismuthate
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depends on the concentration of H2O2
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deltaH
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Hi Blogfast,
Thanks for the consoling words, it helps and I understand, skepticism with reasoning is good! I want to have my idea picked apart, this might identify
an important point/s going in to trying it out.
Parts of this is unchartered territory and I have doubts about certain aspects that I was hoping to get into a discussion about. This doubts might
simple just remain until experimentation confirms or not, but sometimes someone might just point out something that's easy to see is a problem.
That said, the one thing I have very little doubt about is the overall thermodynamics, so lets get back to that for starters...
C3H8O3(l) + 3O2(g) + H2O2(l) => 3CO2(g) + 5H2O(g)
You can calculate a dG(reaction) for this overall equation. The answer is...
[(insert expletive here)... NIST chemistry web book site is closed on account of US gov shutdown... what a pain!
Ok, now I have to do it the long way and trawl for dHf and dSf anywhere else on the open literature...]
HOORAY, a paper online that had everything I needed and more (See attached).
NOTE though they made an error with their dGf CO2, so I recalculated dGf = dHf -T*dSf with T = 298.14K and correct dGf standard CO2 = -457kJ/mol)
Done... dGrx = -1663 kJ (per mole. C3H8O3 as per equation above)
OK, so the reason I've worked this out is because this is thermodynamically the maximum work that can be extracted from my system in
the unlikely event of no other losses (see later points where I include these terms and consider the minimum work derivable).
Now, what I think some people are worried about is that inefficiencies will muck things up in the two internal steps.
BUT, this dGrxn must happen if you reacting those reagents overall.
that energy MUST be released in some way shape or form.
So dGrx = Work done (as generated electricity) + Heat generated (as losses)
My point is this can only be on the right hand side of the equation because dGrx < 0 and Heat losses can never exceed Work done as generated
electricity or you will be claiming your reaction generated more heat than what is thermodynamically possible
Now that said, if you operate with your extreme best to maximise inefficiency, you will minimise the net electricity that can be generated by the
system and maximise heat losses, but in reality this can only be some fraction of dGrx because this is thermodynamically the maximum energy change (in
all forms that may be produced) that can occur!
Now, the best you can do in generating heat is to react those components directly with a heat sink at 25C.
This would be the dHrxn at 25C... I can work that out for you quickly, it's
dHrxn = -1532 kJ/mol (as per equation above on glycerine basis)
So Wmin = electricity min = dG(rxn) - dH(rxn) = -131kJ/mol
So you see, even if you extract absolutely the maximum heat thermodynamically possible from that reaction, your fuel cells minus electricity consumed
by electrolysis will STILL have an electricity production of -131kJ/mol!
Why is this? Because electrochemistry can derive work from the entropic changes as well which a purely enthalpic change cannot (such as simple self
heating).
Interestingly enough, I noticed that that published data had an error for dGf standard CO2 because when I first worked this out, dHrxn was larger than
dGrxn and I knew that this is thermodynamically impossible which lead me to hunt for an error and I found it in the dGf of CO2!
Finally, that when considering the overall thermodynamics, this is path independent of what occurs internally! If you go from A to B, it doesn't
matter thermodynamically overall if you went A to C to D then back to B. You still still consider overall change A to B as the net effect.
This is why it's easy to disprove free energy systems, for example in the case of some car claimed to be running on water:
The overall reaction is:
Water => Water
so dGrxn = 0
So maximum thermodynamic work derivable is when heat losses = 0 so dGrx = Work + heat losses =>>> dGrx = W =>>> W = 0 QED.
Nicodem, can you now understand why I was so insulted by your claims that I was proposing a free energy device?
Okay, that was a mouthful... sorry for the long text, but if we're going to do this properly, we need to do it properly lol
Blogfast25, are you happy with that bit now, can we close that portion off and move on to other technicality problems in this concept? If not then I
can try and prove it from another angle, but please do state what you are unhappy with in my reasoning or I won't know where to start.
Thanks.
Attachment: thermodynamicdata.pdf (1004kB)
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[Edited on 4-10-2013 by deltaH]
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