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Polycaracid
Hypothetical low-power carbon sequestration | |
I made up the word "polycaracid" (major accent on the third syllable; the "cara" part should be pronounced so it rhymes with "para" as in "parachute"), and I'll define it in due course. First, let me describe some general stuff about "polymers".
A polymer is a long-chain molecule, often containing
millions of atoms. It really is chain-like in its structure, typically less than a dozen atoms wide. When a polymer is manufactured, the ingredient chemicals are usually called "monomers". Monomers have a special property that allows them to link together to form a chain, and it is that special property I'll describe next.
The key thing that makes it possible for a chemical to be a monomer, able to form chains, is a "double bond". One of the simplest monomers is called "ethylene" --if you have ever heard of a plastic called "polyethylene" then you can see where the name comes from. The chemical structure of ethylene can be portrayed like this:
H2C=CH2
there are two hydrogens at the left, attached to a carbon atom, and two hydrogens at the right attached to a second carbon atom, and the two carbons are connected by a double bond. When polyethylene is manufactured, the double bonds of many ethylene molecules are broken and reassembled:
....H H H H...
...-C-C-C-C-...
....H H H H...
It is not so easy to portray that with mere text; each carbon connects to two other carbons with one bond each, and each carbon still is connected to the pair of hydrogens that it originally started with.
The key fact, relevant to this Idea, is that EVERY polymer requires a monomer that contains at least one double bond. In theory, then, carbon monoxide is a potential monomer: C=O could beome -C-O-C-O-C-O- ... The problem is that the carbon-oxygen double bond is a pretty strong bond, so it is not easy to break a lot of those bonds and see if a polymer appears when the bonds reform.
Since this is the HalfBakery, I will assume that a method can be found to polymerize the carbon-oxygen double bond.
Since this Category is about Global Warming, I now need to focus on the accused culprit, carbon dioxide (carbon monoxide is a useful fuel, so no reason to try to turn it into a polymer when we can simply burn it to get energy).
Carbon dioxide has two double bonds: O=C=O. In an earlier Idea "Poly CO2" (see link) I described trying to polymerize this stuff in order to make a substance that might be harder than diamond. Such polymerization has since proved to be possible but useless; the stuff is not stable at ordinary pressure (but it DOES mean that that carbon-oxygen double bond CAN be polymerized!). That means we cannot try to use that Idea to directly convert carbon dioxide gas into a solid subtance (a polymer) that is not in the atmosphere contributing to Global Warming.
However! There is a tantalizing variation on the theme. When carbon dioxide and water are mixed together, a substance spontaneously forms (no energy input required!) that is known as "carbonic acid": H2O+CO2->H2CO3. Its structure is: O=C-(OH)2. One of the carbon dioxide molecule's double bonds, with a single oxygen, is replaced by two single bonds, with two oxygens, and each of those oxygens gets one of the hydrogens that was in the water molecule. The other double bond of the original carbon dioxide molecule is untouched.
That double bond means that carbonic acid is a potential monomer, and of course I'm calling the resulting hypothetical polymer "polycaracid". To fight Global Warming, then, this Idea proposes that at any place where large amounts of CO2 is produced, the gas should be mixed with enough water to form lots and lots of carbonic acid. Then we purify it (possibly by freeze-drying) and polymerize it (the hard part!!!) into an easily-piled-up solid, to keep that CO2 out of the atmosphere. Depending on the physical properties of polycaracid, it might even be a marketable substance, like other polymers (typically called "plastics").
Note that the process of polymerization can sometimes be assisted by a catalyst. (When that first double bond breaks in making carbonic acid, WATER is the catalyst that breaks it!) I called this a "low power" approach to carbon sequestration because if a suitable catalyst can be found, to polymerize carbonic acid, then it really would not take a lot of energy to convert carbon dioxide gas into a sequesterable solid (at least, not when compared to some of the other approaches).
Poly-CO2
Poly-CO2
An old Idea mentioned in the main text. [Vernon, Feb 15 2010]
Polycarbonate
http://en.wikipedia.../wiki/Polycarbonate
An anno mentioned that this is a rather complex molecular chain. [Vernon, Feb 17 2010]
CO2, H2O, and carbonic acid
http://www.newton.d...hem99/chem99661.htm
Some information about water being a catalyst for both the formation and the decomposistion reactions. [Vernon, Feb 17 2010]
Pop Rocks candy
http://www.retrothi...xploding_candy.html
It occurs to me that something like polycaracid might exist in there somewhere...certainly if it decomposes when wet, and the only result is carbon dioxide and water, it will be technically edible/safe. Perhaps we could sequester CO2 by making millions of tons of Pop Rocks, and stockpiling it! [Vernon, Feb 17 2010]
Making Pop Rocks
http://en.wikipedia...Rocks#Manufacturing
Nope, no polycaracid here.... [Vernon, Feb 17 2010]
Carbonic Acid article
http://en.wikipedia.../wiki/Carbonic_acid
Wikipedia indicates the pure stuff is probably not stable at room temperature. That's OK, we can sequester it in containers at the South Pole. [Vernon, Feb 17 2010]
[link]
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(+) Without that catalyst would it be an expensive process? |
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A catalyst tends to reduce the energy requirements for a reaction, and if energy is expensive.... |
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An important point that others don't seem to be thinking about, in terms of carbon dioxide sequestration, is that most of the CO2 in the air comes from our efforts to generate energy. If it takes a lot of energy to get CO2 out of the air, then a point could be reached where it would be smarter and simpler to just not burn carbon compounds for energy in the first place! |
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I'm hoping, for this Idea, that the most expensive thing will turn out to be the purification step, of carbonic acid. In the presence of water the stuff breaks down as easily as it forms (water-as-a-catalyst assists BOTH reactions). That's why I suggested freeze-drying; water has different properties in the frozen state than in the liquid state, and we need its catalytic ability to STOP, if we are to purify just-formed carbonic acid from the mixture with water. |
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I think your proposed polymer is unstable. It presumably
has hydrogens filling the vacant bonds, ie: |
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and I am 99% sure that the oxidation ([CH2-O]n+{n/2}02 ==>
nCO2 + nH20) will be very exothermic. (Polycarbonate
burns nicely, and is not that different from what you
propose). |
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In other words, your energetics are screwy from the start. |
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So, you're going to have to pump in lots of energy to make
this stuff. |
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Then there's the question of how stable it is. I don't know
the answer to this. However, the fact that nobody seems
to have encountered this stuff suggests that it isn't stable. |
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I think it's unlikely to be a good idea. If you're going to put
lots of money and energy into making a carbon-rich plastic
from CO2, why pick this one which is probably unstable?
Why not just make polycarbonate or something? |
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[MaxwellBuchanan], polycarbonates are much more complicated than the name implies (and contain lots of carbon-carbon and carbon-hydrogen bonds). Look 'em up. There are NO carbon-carbon or carbon-hydrogen bonds in polycaracid. |
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Yes, I'm aware that polycaracid might be unstable. I'm sure that if it took significant energy to make, THAT would be the energy that could be released during an "instability" incident. On the other hand, the goal here is to replace a double bond between carbon and oxygen with two single bonds between carbon and oxygen, and it happens that usually two single bonds are more stable than a double bond (which is why most polymers are fairly tough molecules). The energetics are typically very similar (which is why the first double bond of a CO2 molecule can so easily become the two single bonds of a carbonic acid molecule). |
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The molecular chain you envision is faulty. This is what I'm expecting:
OH .. OH .. OH (ignore dots used for spacing)
-C--O--C--O--C- (using two hypens to reduce crowding in this representation)
OH .. OH .. OH (ignore dots used for spacing)
Each carbon is attached to four oxygens (two of them are actually OH groups). The chain will be quite crooked because each carbon is at the center of a tetrahedron, not the center of a plus-sign. The two bonds of each oxygen prefer to form an angle, also! |
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To my mind the more likely "instability" problem with polycaracid is the large quantity of attached OH groups. They could be fairly reactive (they are the things that make carbonic acid an ACID). To be determined.... A second sort of instability might be discovered if polycaracid gets wet (exposed to water)--it might spontaneously decompose back into carbon dioxide and water. However, if we keep it dry, we could accumulate quite a pile of solid substance that contains CO2 that is NOT in the atmosphere, and thereby is not contributing to Global Warming. |
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I suspect the biggest problem here, with respect to making it, is that if it works, then each carbon atom will be surrounded by and attached to 4 oxygen atoms. Well, carbon atoms are relatively tiny and oxygens are relatively large; there might simply not be enough room for the oxygens to fit properly! This would increase the amount of energy needed to force that arrangement to exist. |
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I think a little basic calculation on bond energies will tell
you a lot, Vernon. |
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What you're making, then (and yes, I didn't realize you had
hydroxyl side-groups), is basically something like an ether
and something like an alcohol, both of which are pretty
combustible (apart from any activation energy issues
which determine stability). |
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The reason that burning just about anything with carbon
and hydrogen in it makes CO2 and H2O is that they are
phenomenally stable. I'll bet you £999.99 that your
polymer, even if it's kinetically stable, is
thermodynamically unstable and will require a huge energy
input to synthesize. |
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You can also go on any of the chemical structure databases
and search for similar structures, if you need more
clarification. |
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[MaxwellBuchanan], the whole point of this Idea is a kind of extension of the perfectly natural and EASY formation of carbonic acid from those very stable molecules, CO2 and H2O. I wondered about the energetics of it for years, before learning that OTHER water molecules catalyze the reaction. |
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So, we have one C=O double bond that is naturally/easily broken into two C-O single bonds, and all I'm proposing, for polycaracid to exist, is that we make it happen again, with the other C=O bond that existed in each original carbon dioxide molecule (and now exists in the carbonic acid molecule). Until somebody actually tries it (or maybe runs lots of computations simulating it), we probably won't know just how much energy is required to cause it to happen. Meanwhile, this is the HalfBakery, an appropriate place to discuss such things...and you are still confusing things; esters and alcohols can have lots of carbon-carbon and carbon-hydrogen bonds, and there are none of those here, as I said in my last anno. Carbonic acid is a completely-combusted substance! --And polycaracid should be, also...(I actually expect it will be more rock-like than plastic-like, but it still might have some marketable uses). |
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Interesting points, but I haven't been able to find anything
with a C-O-C-O backbone of the type you envisage, in any of
the chemical databases (though I can't claim to have checked
them all). |
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Either it's stable or it's not, and my bet is that it's not (if only
because someone would have made it if it were). Have you
spoken to any chemists? |
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OK - answer from my chemist buddy (who is in charge of
organic synthesis at my lab) is: |
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"any carbon bearing 2 hydroxyl
groups is simply the hydrated form of a carbonyl, which are
usually
unstable reverting back to the carbonyl by loss of water" |
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in other words, your [C(OH)2-O-]n is going to decompose
into [C(O)-O-]n + nH20, which makes sense. And [C(O)-O-]n
looks to me like the bastard child of a ketone and an
ether. |
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Have asked him about the stability of the breakdown
products too. |
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Well, polymerized carbon dioxide (see Poly-CO2 link) would consist of -C-O-C-O-C-O- chains in three dimensions, much like quartz is -Si-O-Si-O-Si-O- in three dimensions. The fact that Poly-CO2 has been made proves that the chain can exist; the fact that it is unstable may indeed also apply to polycaracid, even though here we only want a one-dimensional chain. So, is the difference between Poly-CO2 and polycaracid different enough for the latter to be stable? I don't know. But then, posting notions like that is what the HalfBakery is for, so.... |
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One variation of this theme, like the manufacture of polycarbonates, is to make a polymer from two different monomers, not just one. For example, if silicon dioxide could react with carbonic acid in a special way, the result might be:
SiO2+H2CO3-->H2SiCO5
Molecular structure would resemble:
OH . O . . OH . . . . OH . O (ignore dots)
-C-O-Si-O-C-O-Si-O-C-O-Si-O
OH . . . . OH . O . . OH
There are three H2SiCO5 units above.
Each silcon gets a double-bond with an oxygen, and has a single bond with two other oxygens. Each carbon still has 4 single bonds with 4 oxygens. There are lots variations of this theme possible of course. One of them, without even involving some substance other than quartz, might be this:
OH . .O. .OH . . . . OH . O (ignore dots)
-Si-O-C-O-Si-O-C-O-Si-O-C-O
OH . . . . OH . .O. .OH
This keeps the double bonds with the carbons, but moves the OH groups from the carbons to the silicons --or more accurately, moves hydrogens from oxygens attached to carbons to oxygens attached to silicons; the strength of the OH bond remains unchanged. |
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Like I said, lots of possibilities... |
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//The fact that Poly-CO2 has been made proves that the
chain can exist// What? Your link points to your other poly-
CO2 idea - is there a link from there that shows synthesis of
poly CO2? |
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And yes, there are lots of possible ways to incorporate CO2
and its derivatives into various polymers. But I'm still
prepared to bet that you need to pump in a lot of energy (as
energy or as reagents) to synthesize them. |
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Also Chemist Man just got back about the stability of the
breakdown products of your "polycaracid": |
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"well a chain of (CO) is highly unlikely to be stable,
preferring to
eliminate water and break down again. of course if you are
talking about
gas phase or some artificial situation then it may be that
short chains
could exist......." |
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There is an "Apparently Now Discovered" link in the Poly-CO2 page. The "CO2, H2O, and carbonic acid" link on this page indicates that pure carbonic acid is fairly stable if water is kept away from it. That's why I've talked about keeping water away from the proposed polycaracid. |
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I'm sure Chemist Man (link please?) has a point, but it seems to me that that point depends on the detailed molecular arrangement. That is, for water to spontaneously be released, one oxygen atom needs to be in close proximity to two hydrogens. I am thinking the 3D molecular structure may not be so accommodating. (Now where can I find some little balls and sticks to make a model....) |
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Heh, after all this discussion it FINALLY occurred to me to wonder if pure carbonic acid is a solid or liquid or gas. If not a gas, then no polymerization is needed; just tank it up and keep it away from water! |
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//Chemist Man (link please?)// Link? He's a person, not a
website. He runs organic synthesis at the MRC Laboratory of
Molecular Biology. Hang on while I check your link. |
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Re your link, whoa - hold on a second. First, they are talking
about an allotrope of CO2, not a polymer. Second, it's stable
only at huge pressures. So no, it's not "apparently now
discovered". |
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Hey, I SAID in the main text here that Poly-CO2 is not stable. And in case you don't know, glass and quartz are allotropes of SiO2 (provided the glass has no other additives). Also, in case you don't know, a polymer is NOT ALWAYS ONLY a one-dimensional chain of atoms. Quartz and glass are both polymers! Both allotropes involve large 3-dimensional structures of connected atoms. |
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Graphite consists of a stack of 2-dimensional sheets; graphite is an allotrope but each sheet is a polymer of pure carbon. Diamond is a 3-dimensional polymer/allotrope of pure carbon. |
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So, a glassy version of Poly-CO2 is still going to contain polymerized carbon dioxide, in the form of large 3 dimensional structures. The data at the link IS good enough to be able to say that polymerized CO2 can indeed exist. |
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I can polymerize chickens at high enough pressures too,
but that's not the point. |
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The point is that, as far as anyone can tell, you can't
create a polymer of CO2 which is stable under reasonable
conditions. |
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Also, for your scheme, you've got to get the CO2 out of the
air. I'll guarantee that it's far more efficient at that stage
to just liquify it in big pressure vessels and leave it
somewhere (like Basingstoke). |
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I think this is bad science, but interesting discussion. |
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[MaxwellBuchanan], the point of this particular Idea is NOT about polymerizing pure CO2; it is about polymerizing carbonic acid. I have been quite aware all along that the problems with Poly-CO2 might be relevant in terms of causing problems for hypothetical polycaracid; that's why I've used the word "hypothetical" frequently here; haven't you noticed? |
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Next, you have apparently ignored the part of the main text where it talks about capturing carbon dioxide AT THE SOURCE and using enough water so all of it becomes carbonic acid. This is tremendously less expensive than trying to get it out of the air (but not impossible since ANY water exposed to air naturally dissolves some of the CO2 in the air, forming at least some carbonic acid). |
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The major expense will be in the purification steps. After that, if pure carbonic acid is a liquid or solid, then polymerizing it is moot/unnecessary; we can sequester it directly in that form. (My guess, based on its molecular weight and structure, is that it will be a hydrogen-bonded solid like water-ice.) Only if it is a gas do we still have an issue regarding getting it into a more-sequesterable form. Polymerization may not be the answer. But I'm becoming more and more convinced that making lots and lots and lots of carbonic acid is the cheapest/best first step to reducing the biggest human contribution toward Global Warming. |
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OK - yes I did miss a couple of points - my apologies. |
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But the core of this idea was to create a polymer, which I
still think is energetically unfeasible. Storing carbonic acid
might be possible under the right conditions, but again I
suspect that just storing it as a solution will be the only
practicable way (and what is wrong with that? water is
cheap and available), in which case the scheme boils down
to capturing CO2 in solution, which is a fairly well-known
idea (I think). |
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Anyway, [-] for some of the chemistry, [+] for the
discussions and thoughts provoked, so [ ] overall. |
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As long as it takes less energy to create the polymer than is extracted from the coal (per carbon atom), this idea would be energetically (if not economically) feasible. This might mean having to burn 5 times as much coal to create the same net amount of energy, but if zero carbon emission is your goal that would be OK. |
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Could someone summarize what research has already been done on polymerization of carbonic acid. Looks like there's some stuff out there but I have no idea how relevant it is, or how it differs from, the present idea. |
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[MaxwellBuchanan], it is essential that any stored carbonic acid be very pure, at the very least totally "anhyrdrous". That's because just one molecule of water is sufficient start catalyzing the breakdown of carbonic acid back into CO2 and H20. The whole point of getting CO2 OUT of the gaseous state is so that large quantities can be stored in a small space at ordinary pressure. You could have a serious explosion if pure carbonic acid is exposed to water, like storing pressurized liquified CO2 and then letting it warm up.... |
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Yes, but storing pressurized CO2 as a liquid is routine (I'm
within 100 metres of at least half a dozen cylinders thereof).
So, given the predicted difficulty in preparing and storing
very large amounts of carbonic acid without even a single
water molecule present, why not just store liquid CO2? |
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Sorry, I may be missing something here, in which case my
apologies. |
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In terms of total costs, refrigeration and pressure vessels would add up to greater cost in the long run, for pure liquid CO2, vs anhydrous carbonic acid. |
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How did you calculate that? You only need a compressor,
and possible a refrigeration unit, at the bottling stage.
After that, you have a sealed steel cylinder that needs no
further refrigeration. |
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Is this really going to be more expensive than preparing
carbonic acid, distilling it to remove every *molecule* of
water (remember - even one will start a chain reaction),
and then keeping it completely watertight? |
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I might be wrong, but show me the numbers on that. |
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This is a seductive topic. I think that if one is limited to only C, H and O in making polymeric carbon, the O is the problematic piece because of the tendency to decompose to H20 and C02, as has been mentioned. |
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If one could polymerize carbonic acid into fullerenes or diamonds or graphite, that would be a nice and permanent way to sequester the carbon. |
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[MaxwellBuchanan], refrigeration costs energy. That means ANY storage system that relies on refrigeration will cost more in the long run than one that doesn't, regardless of up-front expense for that non-refrigerated method, if "long run" is long enough. OK, so I didn't know that pressurized CO2 didn't need additional refrigeration. That's good, but compare the cost of millions of strong and rustproof steel tanks of pressurized/liquid CO2 to millions of buried plastic bags (which can last for many centuries according to environmentalists!) holding solid or liquid anhydrous carbonic acid at normal pressure, and I still think that in the long run storing carbonic acid will be cheaper. |
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[bungston], please note that fullerenes and graphite and diamond are all pure carbon. You have to add energy to CO2 to get the carbon separated from the oxygen (as much energy as you got when coal was burned, and more when one includes inefficiencies). This Idea is not at all about separating carbon from oxygen; it is about modifying C=O and C=O double bonds to become a -C-O-C-O- chain of single bonds. We know that the energy required to do PART of it is trivial, since one double-bond of CO2 does it spontaneously when CO2 is added to water (one oxygen remains double-bonded, the other oxygen switches to a single bond, and an extra oxygen, singly bonded, comes from a water molecule). It is reasonable first-approximation to think that only a modest energy requirement would be associated with converting the other double bond, so long as the carbon, that started inside a CO2 molecule, remained connected to oxygen only. |
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[vernon] re. storage costs, you can buy steel pipe in any
reasonable diameter which can be of any length you like,
at very low cost - just cap each end and have a filling
nozzle at one end, and your costs for storing liquid CO2 are
very low. |
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In contrast, I would pretty much guarantee that it is
**impossible** by any known means to prepare a litre of
anhydrous carbonic acid and a container to hold it, which
are both free of water *down to the single molecule level*.
And, again, even a single water molecule will start a chain
reaction which becomes two, four, eight...bang. |
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For example, *all* manufactured plastics contain some
degree of water (measured, often, in parts per billion or
per trillion), which are in there either as chemical
products of the polymerisation, or as residuals in the
feedstock, or are simply absorbed from the air during
manufacture. This means that a 1 litre container will
contain vast numbers of water molecules, of which at least
one will escape into your carbonic acid. |
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It's a bit like trying to remove every single individual
bacterium from a small island (and we can't even get an
operating theatre anywhere near that clean). |
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[MaxwellBuchanan], you are being too pessimistic. See the "instability" section inside the linked Wikipedia article on carbonic acid. Also, industy typically uses substances known as "getters" when they want to focus on removing some particular chemical from an environment. And I didn't say what sort of plastic bag; some have less water than others, I'm certain. "Where there's a will (and money, of course), there's a way." --USUALLY. Few things are actually totally impossible. Not to mention you seem to be forgetting that this IS the HalfBakery.... |
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Fair point about the getting with getters, and this indeed
indeed the ery. |
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Anyway, I was curious to know how much energy is
required to compress 1ton of CO2 into liquid. I couldn't
find a figure for this, so I assumed the worst-case scenario,
where the energy required is simply the energy needed to
compress the gas by 3000-fold (since this is the relative
volume-change in going from gas to liquid). |
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So, 1ton of CO2 gas at stp has a volume of 500,000 litres, or
500 cubic metres. At room temperature, CO2 becomes
liquid at about 40bar of pressure, so I'm basing my rough
calculation on the energy needed to compress 500 cubic
metres of CO2 to a pressure of 40bar. |
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Based on this model, the energy required is about 1GJ. |
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This seems a lot, until you realize that (a) this amount of
CO2 comes from the burning of about 300kg of coal, which
yields about 10GJ of energy and (b) almost all of the
energy which is put into compressing the CO2 is given out
as heat (ie, the CO2 will get extremely hot as it is
compressed), and most of this energy can be recovered
and used for power generation. |
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So, simple liquefaction of CO2 at the point of production is
very simple and costs a moderate but affordable amount
of energy. |
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That is the target you have to aim for, and I don't see you
getting there easily by trying to convert CO2 into a large
amount of an extremely pure compound which has so far
been produced, in pure form, in minuscule amounts by
very sophisticated methods, and which is inherently
unstable w.r.t. water. |
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[Vernon - can you do an end-of-a-backelope calculation on
the energy needed to convert 1ton of CO2 gas at s.t.p.
into pure carbonic acid?] |
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We also seem to have completely lost the "polycaracid"
theme somewhere.... |
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Incidentally, the annual production of CO2 is something
like 30 billion tons. This is about 5 tons for every person. |
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I think (I am not sure here) that the little Sodastream
cartridges are liquid CO2. This means that, if we were
each prepared to store 5 large crates of Sodastream
cartridges per year, we could save the planet. I for one am
happy to play my part here. |
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On the other hand, all this stuff reminds me of the
discussions on how to avert the Y2K catastrophe. |
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//DISC// ? Is that some kind of LTLA? |
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Carbonic acid is stable with a cation - for example with calcium it makes carbonate rock. Absent the addition of some anion to make up for wouldn't polymerizing the carbonic acid into a nonionic form lead to an excess of H+ ion until the energetic became unfavorable? |
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I posted an anno to one of Vernons other schemes about using the earth's iron to serve as the cation and sequester CO2 as carbonate. Actually it incorporates NaCl from seawater, with the CO2 sequestered as sodium bicarbonate and the chlorine reacted with elemental iron. "The chlorine could be tied up with iron (FeCl2), and sequestered in the same underground repository. I think those two should be stable together." They would be stable together somewhere dry. Maybe Yucca Mountain if they aren't going to keep the nuclear waste there. |
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I was thinking about what the properties of some rare earth catalysis that polymerized carbonic acid. Aside from whatever properties polycaracid might have, I think this catalyst would be very poisonous Multicellular life regulates pH closely, and generally through manipulations of carbonic acid. Of course lots of catalysts are poisonous but there would need to be a lot of this one given the scale of the project. |
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[MaxwellBuchan], I don't mind getting off the topic of polycaracid if we don't need to talk about it; it is hypothetical and its stability issues require investigation before the Idea can be taken seriously. |
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Meanwhile, we both recognize that before one can make polycaracid in quantity, one needs a quantity of carbonic acid. So, discussing that is still relevant. |
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Regarding an energy cost, the main cost is the purification step. I'm fairly sure that ordinary distillation (which you possibly mentioned in another anno) won't work; it will cause the carbonic acid to break down. That's why I mentioned freeze-drying in the main text. Note that this process is known to remove water to a very high degree of completeness. |
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Only the energy of running heat pumps is necessary to freeze a quantity of carbonated water. This should be similar to the quantity of energy needed to pump heat such that one can liquefy CO2, and it is somewhat recoverable, as you also indicated. |
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[bungston], the problem with providing a cation, to make a carbonate, is that first the cation USUALLY needs to be separated from whatever anion the thing is normally found associated with in Nature, and that can be an energy-intensive process (not cost-effective on the scale of millions or billions of tons per year). Sure, if you could get at the Earth's nickel-iron core, you would have lots of already-fairly-pure cation available --but we don't have access to that, and aren't likely to get access in time for it to be useful for this Idea. Sorry. |
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//OH . O . . OH . . . . OH . O (ignore dots)
-C-O-Si-O-C-O-Si-O-C-O-Si-O
OH . . . . OH . O . . OH // |
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Gee, folks, it only took almost a year for me to think of the notion that if we start with lots of CO2, and add a modest amount of water (instead of adding modest amounts of CO2 to lots of water), then it should be possible for practically all the water to get used up in combining with the CO2 to make carbonic acid. That should then make the removal of the last bit of water a relatively small task! |
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The net result, then, would be a fair quantity of carbonic acid surrounded by an atmosphere of CO2. Which we keep together as we package it for our sequestration pile (or hole in the ground). Then we fill the reaction chamber with another large batch of CO2, and add another modest amount of water... |
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What's the equilibrium constant between CO2+H2O <=> H2CO3
? I didn't think it was the right way for this to work? (What
you are talking about, basically, is making soda water.) |
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[MaxwellBuchanan], the tangy taste of soda water IS the taste of carbonic acid. At the moment all I can say is, the colder the water the more CO2 can dissolve into it. I don't know how the temperature affects the rate of catalytic formation of carbonic acid, though. While a colder temperature might slow the rate of production, it should also slow the rate of spontaneous breakdown. Which wins at near-ice temperature? I don't know. |
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Hi Vernon. Exactly - that was my point. The equilibium
constant is pretty far over in the wrong direction. If you mix
equimolar amounts of water and CO2, you don't get a lot of
H2CO3. That's why your soda fizzes. |
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You're up against reality, sadly, and it carries a big stick. |
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[MaxwellBuchanan], you are ignoring the "pressure" factor. They make soda-pop by subjecting flavored water to lots of pressurized CO2. Besides increasing the amount of gas that dissolves (just like other gases can dissolve in water), it also increases the amount of carbonic acid that can form. I'm quite sure that ordinary soda-pop manufacturers aren't interested in maximizing the amount of carbonic acid that gets made, so they haven't experimented with extreme pressures. I don't know who has.... |
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Yes, you can certainly increase the solution of CO2 into
water (and, very probably, the content of carbonic acid). |
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In fact, if you whack up the pressure enough, you can get
100% CO2 as a liquid. |
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If you do a little in-depth research (Wikipedia) you will see
that, at 10 atmospheres, CO2 dissolves to about 0.3M (ie,
something like 1/100th the mass of the water it dissolves
in). Carbonic acid, at this pressure, is at about 0.6mM
(about 0.03 grams for every litre of water). Things go more
or less proportional with pressure (at least up to some
point), so if you can get up to 100atm of pressure, you'll
get about 0.3 grams of carbonic acid for every litre of
water. |
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Anyway, who says that basic laws of chemistry and physics
have to get in the way of an idea. Go bake - bring me back
a lump of polyracid. |
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I think that were there sufficient ammonia as a byproduct, even with a less than perfect catalyst within an exothermal production climate, the product would be profitable and green. bun. |
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If it also made the tea and left your skin feeling softer, it
would also be bunnable. Sadly, it will do none of these
things. |
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Where exactly were you hoping that the nitrogen would
come from? |
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MB, I was going to whale on this idea, but I see that you have beat me to it. Good work man. This is why a year of chemistry should be a graduation requirement. If C-O-C-O-C was a stable bond formation then the entire chemistry of life would be completely different. |
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"if silicon dioxide could react with carbonic acid in a special way, the result might be" ...... a disaster for sand and the abandonment of glass bottles for carbonated beverages. |
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[WcW], your own knowledge of chemistry needs improving. Ordinary silicon dioxide is an already-polymerized substance; there are few if any double-bonds between oxygen and silicon atoms in that three-dimensional-long-chained molecular network. |
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However, hypothetically, it should be possible for a pure monomer form of silicon dioxide to exist, equivalent to the ordinary CO2 molecule. That SiO2 monomer would quite certainly be able to polymerize easily, as proved by the probable difficulty of being able to depolymerize the natural polymer, to make said monomer. |
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But after you obtain some, can that monomer-SiO2 polymerize with and within a mixture of other monomers (such as carbonic acid)? THAT is the question! Note that the ordinary glass soda pop bottle is already-polymerized SiO2, and that's why there is no significant interaction with the carbonic acid in soda pop. |
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I seriously don't see any of this chemistry working, but only
for fundamental reasons. |
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// I can polymerize chickens at high enough pressures, but that's not the point. // |
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// I don't see any of this working, but only for fundamental reasons. // |
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// Where exactly were you hoping that the nitrogen would come from? // |
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The atmosphere is ~70% nitrogen. |
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