Sciencemadness Discussion Board

News Story: Gasoline From Air

Boron Trioxide - 26-10-2012 at 17:36

I noticed this very interesting article and haven't seen it on sciencemadness. It seems to involve producing gasoline directly from carbon dioxide and hydrogen. I have no idea how this would be done, though what are your thoughts?

http://www.independent.co.uk/news/uk/home-news/exclusive-pio...

12AX7 - 26-10-2012 at 17:46

Hmm, it was posted under Whimsy:
http://www.sciencemadness.org/talk/viewthread.php?tid=21858
of course you'd need access to see the link...

Tim

chemrox - 28-10-2012 at 15:55

There's nothing knew about making fuels from basic materials. In WW II the Germans made tankers full of diesel from CO & H2. It's doing it in an economically favorable way that remains the challenge (as the story says.)

Conrad - 14-11-2012 at 03:21

What the germans used was the CTL(coal to liquid) process. First a steam reforming process to convert CO together with H20 into CH4 and then the fischer tropsch-synthesis, or more to say a very basic form of this. It forms longer carbon chains in the C8-C12 region which can be steam-cracked to smaler fractions and then distilled. (at least this is what they do at SASOL and SHELL in their GTL(gas-to-liquid) processes)
What a group recently found is a catalyst that is able to minimize the energy needed to break down CO2 into (I think I actually read about CO). But at a very low rate, and maybe with additional energy needed. From this point one could go with the FT-Process mentioned above.

Think about this:
You fuel up your car and burn it in a highly exothermic process into CO,CO2 and water basically.
So the back reaction has to be highly endothermic but the reaction energy can be lowered by using a catalyst.
Now imagine how powerful this catalyst must be :-)

tetrahedron - 14-11-2012 at 03:39

Quote: Originally posted by Conrad  
the back reaction has to be highly endothermic but the reaction energy can be lowered by using a catalyst.
Now imagine how powerful this catalyst must be :-)

that's incorrect. a catalyst can in no way change the thermodynamics of a reaction. this is completely defined by the balance between products and reactants, and a catalyst is neither. it can help e.g. reduce the temperature and get an efficient process, but the necessary energy still has to be supplied.

Dr.Bob - 14-11-2012 at 12:09

Yes, there is no such thing as a free lunch or a free fuel.

The energy needed to create gas/fuel from air/CO2/whatever will ALWAYS be more than the energy released when it is burned (nuclear processes excluded). Nothing creates energy from oxidized material (CO2/water/urine(see below)) without some input of more energy.

A similar article was seen recently, claiming that urine could power a generator, which upon closer examination simply showed that water can be electrolyzed to hydrogen and oxygen (using a substantial amount of electric power) and the hydrogen can be burned to generate less power than was put in. I get tired of people "proving" that you can "create" energy when they are simply converting it from one form to another without realizing that that process does not create energy, it only changes it, and typically is very inefficient.

http://news.yahoo.com/blogs/sideshow/urine-powered-generator...

Urine is put into an electrolytic cell, which separates out the hydrogen

smaerd - 14-11-2012 at 14:19

I have heard of attempts using electrolysis to turn CO2 into methanol never gasoline. But this is neat thanks for sharing.

franklyn - 14-11-2012 at 18:04

Oxidation of methane is considered an irreversible reaction

CH4 + 2 O2 => CO2 + 2 H2O

An effective method for efficient reforming is wanting.


These are known reversible reactions

CO2 + 4 H2 <=> CH4 + 2 H20

CO + 3 H2 <=> CH4 + H2O

CO2 + 3 H2 <=> CH3OH + H2O

Catalytic hydrogenation of carbon dioxide to methane
http://web.anl.gov/PCS/acsfuel/preprint archive/Files/17_1_NEW%20YORK_08-72_0011.pdf

Kinetics , Catalysis & Mechanism of Methane Steam Reforming
http://www.wpi.edu/Pubs/ETD/Available/etd-011207-151645/unrestricted/James_Master.pdf


You can see that putting CO2 and 2 H2O on the same side
of equilibrium requires reducing both. The cited article
implies this can be done electrolytically which is reasonable.

Reversible Interconversion of Carbon Dioxide & Formate by an Electroactive Enzyme
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2491486

New Catalyst for Safe, Reversible Hydrogen Storage
http://m.phys.org/news/2012-03-catalyst-safe-reversible-hydrogen-storage.html

.

Conrad - 14-11-2012 at 23:23

Quote: Originally posted by tetrahedron  

that's incorrect. a catalyst can in no way change the thermodynamics of a reaction. this is completely defined by the balance between products and reactants, and a catalyst is neither. it can help e.g. reduce the temperature and get an efficient process, but the necessary energy still has to be supplied.


Let´s say it´s the activation energy that´s lower :-)
The Gibbs-Energy stays.

497 - 15-11-2012 at 06:12

That last article is really impressive franklyn. I didn't realize they'd got it to work in ambient conditions.

In case some of you don't have extra iridium amine catalyst laying around, I present:

http://www.rsc.org/suppdata/ee/c0/c0ee00661k/c0ee00661k.pdf
High-yield reduction of carbon dioxide into formic acid by zero-valent metal/metal oxide redox cycles

Hydrothermal reduction of CO2 with water and a metal like Fe, Zn, etc. Then they reduce the iron oxide back to iron with things like glycerol. No catalysts in the entire process! Super cool. Too bad it hardly made news.. Just way too simple, practical, and "unmanopolizable" for any corporation to risk popularizing??

Screw gasoline, really formic acid is the way to go in many respects. No need to ever deal with H2 gas really. Direct formic fuel cells are the future! It's even more practical than methanol for fuel cells, and it will be easier to produce/transport.

[Edited on 15-11-2012 by 497]

l0k1 - 15-11-2012 at 07:49

someone was talking about thermodynamic equilibrium with CO2... not sure if anyone has heard of oxyhydrogen or 'browns gas', using a stack of alternate polarity steel plates immersed in water and an AC current with i think it's a sawtooth waveform, a gas is generated which appears to be flammable. it's commonly mistaken to be hydrogen and oxygen but there is videos you can see from a company that is developing devices that produce and utilise this gas and the gas rapidly loses its ability to burn when it is in the air for long.

well, anyone who is familiar with quantum electrodynamics would know that there tends to be a relationship between energy thresholds and the addition of either heat/photons or electrons, one goes in, the other tends to come out. like sodium emitting two types of yellow photon when you run an arc through it.

well, my personal theory about what is going on is that the capacitative electrolysis type thing is imparting electrons in the form of an electrostatic charge that neutralises the hydrogen bonds. immediately its vapor pressure drops and it becomes 1860 times less dense, and appears to burn in air. however, what i think is happening is that mixing this electrostatically charged water with carbon dioxide, add a little heat and the electrons go to the carbon dioxide causing it to cleave the oxygen bonds partially allowing a far lower energy threshold to oxidise again and release the heat that was stored when the carbon dioxide formed during a combustion, like a nano-scale heat engine. i believe a similar reduction of the amount of heat required could be produced by using an arc furnace that would also stimulate the CO2 to have electrons ripped off it by the current. it would not be as efficient as being able to bring the electrons a pair at a time right in close with sufficient heat to loosen the double bonds.

the thing is that i haven't got around to making a generator to test my hypothesis about carbon dioxide. i suspect that the mix of the brown's gas and carbon dioxide would function inside a fuel cell to directly convert to electrons from nano-scale surface catalysed oxidation pushing electrons about by releasing photons. however, the more immediate application is in internal combustion engines. it should be possible to place some kind of inline filters on the air intake to concentrate the carbon dioxide and oxygen and reduce the amount of nitrogen because it appears that this reaction is inhibited by nitrogen. Another option is to simply change the fuel to a cylinder with a molar mix of CO2 and O2 or whatever gas mix is the correct combination. I think that it's the carbon dioxide alone, and that once it is cleaved it provides the oxygen for the reaction. There may be some mechanism involving the water and the carbon dioxide going on as well, but by the time it's done its thermal expansion it's all back to ordinary atmosphere.

[Edited on 15-11-2012 by l0k1]

Conrad - 15-11-2012 at 15:47

A little off topic, I found this while searching the article I was referring to, but also very interesting:
http://www.sciencemag.org/content/334/6061/1383.abstractt
"A Perovskite Oxide Optimized for Oxygen Evolution Catalysis from Molecular Orbital Principles"
The main benefit is that they improved the limiting factor in water electrolysis, the evolution of oxygen by an order of magnitude.

Does anybody have interesting information about current approaches in hydrogen storage? Or can give some info in general about H2 storage? I haven´t looked into this during ten years of being a chemist besides thinking "hydrogen´s really tiny"...



12AX7 - 17-11-2012 at 11:14

Brown's gas: http://www.tinaja.com/glib/muse120.pdf and so on.

ElectroWin - 17-11-2012 at 11:53

the various catalysts and circumstances for this reaction (temperature and pressure) tend to favour different products, eg: CH4 versus CH3OH, versus higher alkanes and alcohols