h a l f b a k e r yYeah, I wish it made more sense too.
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Fossil fuels, especially coal, are nice to burn. They make good energy. However if burning continues until it stops, maximally oxidized carbon as CO2 is released. That makes us hot.
With more careful control of oxidization, it should be possible to burn natural gas and coal without releasing fossil
fuels. If oxidation stops at HCOOH, one has formic acid, which is not a greenhouse gas. This acid could be poured into deep cracks in the earth - maybe into the same holes they got the petrochemicals out of in the first place. Nearly all of the energy of the alkane petrochemical is still extracted, but no greenhouse gas is emitted.
This would be easier to do with natural gas than with coal, on account of coal is chunky. The natural gas could be reacted on a catalytic substrate with control of oxygen entering the system. This substrate would need to be magically designed in such a way that formic acid was not a suitable reactant, but all less oxidized carbons were.
to make greenhouse gas into feedstock
http://www.rsc.org/...house_feedstock.asp
[ldischler, Feb 14 2007]
Methane to methanol
http://www.chem.uma...tions/MOchapter.pdf
exothermic: 126 kj/mol [bungston, Feb 16 2007]
Methanol to formaldehyde
http://www.latrobe....8Abs/MoO/MoO-13.pdf
some exotic metal catalysts, again. [bungston, Feb 16 2007]
Oxidative dehydrogenation: methanol to formaldehyde
http://www.springer...t/w9p75839t6520233/
I can't tell if this one is freely available or not. From the text, describing exothermic oxidative dehydrogenation of methanol: CH3OH + 1/2 O2 -> H2CO + H2O: deltaH = -159 kJmol-1 [bungston, Feb 16 2007]
Conversion of formaldehyde to formate
http://cat.inist.fr...cheN&cpsidt=1095307
With gold this time. Greater than 100% efficiency but I had a hard time finding energy output for this one. [bungston, Feb 16 2007]
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"Now Japanese researchers have isolated the active form of a catalyst that turns CO2 into formic acid using water as a green solvent, a crucial step in developing this technology on an industrial scale." -- see the first link |
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I'm afraid you can't just stop the oxidation
here [bungston] - fossil fuels will combust
to form CO2. |
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However, if you do burn the fuel to form
CO2 and then bubble that CO2 through
water, you'll get carbonic acid, which does
not contribute to global warming. You'll
need a catalyst on this though, which
might prove costly. |
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Why can you not stop the oxidation, [jtg]? Or limit its ability to start? Oxidation happens one molecule at a time. |
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[ldischler] that is interesting stuff. I would think it would be more energetically favorable to stop at formate before producting CO2 than to go backwards from CO2 to formate, but that is what catalysts are all about. |
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What are the energetics? ie, what
proportion of the energy of combustion of
carbon or hydrocarbon is released in an
oxidation that stops at formate? |
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This isn't really an idea, more a problem you want to deal with. There's no real method here of making sure the oxidation stops at HCOOH. |
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I know that more energy is released with CO -> CO2 than C -> CO. But that's not helpful: just an indication of likelyhood. |
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once a reaction begins it does not progress in readily definable stages as you suggest. Many times a reaction is written out that way to make it clearer what is happening during the reaction, but in general most reactions of this type are one way affairs that can not be stopped at some stage along the way(as the "along the way" stage doesnt really exist). You cannot undo a combustion reaction so once it begins the only way to stop it is to run out of one or both reagents or achieve a ratio between them that is no longer able to support combustion at which point you will have a definable mixture of un burned hydrocarbons, Air CO2(a little CO as well) and other assorted waste products. |
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You can go to CO2 and then back to the formic acid but that will reguire the addition of energy in some form as this is now a new reaction. |
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There are some reaction pathways that involve a chain of reactions that occur such that if one tweaked the system before the next stage occurs then you could theoretically collect the intermediate. This however is not one of those reactions. |
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Sorry but [Marked-for-Deletion] this is Bad Science. |
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Our own bodies routinely oxidize
carbon incompletely, and stop along the
way because the oxidized product is
good for something else - instead of
formate, a lot of times we stop at
acetate. Or push on thru all the way to
CO2. Similarly, a puddle of gas will
explode if you light it, but control the
ratio of fuel to air and you can have an
internal combustion engine. |
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Essentially what I am proposing is a fuel
cell, but with the catalytic surface
designed to reject formate. There
might actually need to be a number of
molecularly specific catalytic substrates
in such a cell, each corresponding to a
different unoxidized or partially
oxidized component of the fuel. As
stated in the idea, a fuel with a limited
number of components would be better
for this concept. |
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I have never seen a proposition for a
fuel cell that does not completely use
its fuel, but I cannot claim to be that
knowledgable about fuel cells either. |
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I have doubts about pouring acids down deep holes in the ground - sounds like a great way to extract carbonates from rock as CO2. |
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What's the point at stopping at formic acid if you're just going to put it underground? Just burn it completely, recapture the CO2, and put *that* underground. At least if there's a little leakage we're not dealing with millions of gallons of environmentally toxic liquids, just CO2 that can easily be recaptured again and put back down there. |
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Sounds like a really high-tech answer to a relatively low-tech problem. |
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//This substrate would need to be magically designed in such a way that formic acid was not a suitable reactant, but all less oxidized carbons were.// |
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[bungston] Im ashamed at you, you know better than this! |
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As to how our bodies work the reactions taking place in out bodies are operating on long chain sugars and make use of enzymatically regulated multistage reactions and so each stage of the reaction utilizes different enzymes or reactants to achieve its goal, by regulating the presence and amount of the reactants or separating the reactions into different areas of the cell or body our body can regulate how far and how much of different end products are produced. If you chewed up a chunk of coal or drank a gallon of gasoline your body would not be able to generate an energy from it at all as it does not operate on Carbon in the way you envision it. These reactions in the body are also more energy intensive than simple oxidation reaction in the presence of heat, or put another way they produce less overall energy than a combustion process so you would need to use more fuel to get the same amount of power. |
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Fossil fuels on the other hand are a different class of chemical from sugars and as such do not react the same way and cannot be processed using the same reactions. The comments I listed before are still valid. |
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Based on the fact that your idea is based on a "magically designed" substance I will not remove my MFD. |
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Again, what's the energy? There must be a
chemyst amongst us who can tell me the
kJ/mol for oxidising a given hydrocarbon
as far as formate, and likewise for formate
to CO2? Damme if I shan't try and look up
the numbers myself.... |
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[jhomrghaus] - I agree that biological oxidations produce less energy than open combustion: about 50-60%. However a considerable amount of an open combustion is lost to wasted heat - true also but to a lesser extent for biologic systems, but the whole point of constraining oxidation to a series of reactions is to prevent spontaneous combustion of the organism. A good trade. Hamburger gets hot when it burns. |
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I disagree that an alkane is fundamentally different than a sugar. A sugar is just more oxidized. Without a little oxygen we can't get a grip on it, or so it would seem. If we had evolved in a situation where alkanes were abundant, we could probably eat them. Some bacteria do and they are our distant cousins. |
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Oxidation via fuel cell is making fuel use more biological, or that's how it seems to me. As regards magic, when I google for this stuff the vanadiums and molybdenums and ceriums seem sort of magical to me. Metal catalysts are neato. I have linked some to show that the steps in this reaction can be done. It is not always clear to me why these scientists to make these catalysts are doing what they are doing - it seems most have some industrial end for which they are inventing means. |
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