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What About Hydrocarbon combustion WITHOUT CO2?

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napoleon_in_rags Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Aug-14-11 03:36 AM
Original message
What About Hydrocarbon combustion WITHOUT CO2?
So I got curious today, looking into how carbon fiber was made (trying to figure out why it was so damned expensive) and I came upon this chemical reaction for PAN, a precursor of valuable carbon fiber:
2CH3-CH=CH2 + 2NH3 + 3O2 → 2CH2=CH-C≡N + 6H2O
This reaction is exothermic, it outputs no C02 but a lot of heat - the core thing needed to produce energy or turn a motor. The input is propylene (and ammonia). Propylene is a hydrocarbon, another fruit of the oil drum and like the rest its combustible. Its normal combustion equation is
C3H8 + 5O2 ---> 3CO2 + 4H2O
Notice the C02, just like gasoline or anything. But in certain processes like the one I mentioned first, it appears to me that carbon can be outputted in solid forms rather than as C02, (in this case Polyacrylonitrile aka PAN) saving the environment while still releasing energy to turn a motor... (And in the case of carbon fiber production, into an INCREDIBLY valuable industrial compound to boot.)

Now I'm not a chemist or an oil guy, and I can see the reaction I am talking about certainly isn't the answer for powering cars... Papers say it outputs C02 (through a parallel process, not fundamental reaction) as well as such lovely sounding things as "hydrogen cyanide", not to mention ammonia consumption (needed for fertilizer).

Yet the dreamer in me can't help but to notice what a complete and total HOLY GRAIL hydrocarbon combustion without CO2 would be, and this reaction offers a hint that its possible. Imagine: Total reduction of greenhouse gases with no economic cost from limiting fossil fuel consumption. And honestly, this idea seems fresh: I've looked into carbon sequestration, and I see a slew of technologies that seek to actually remove existing C02 from the air, which intuitively hits me as being "putting the genie back in the bottle", more expensive and difficult in every way than not letting the genie out in the first place: having engines output a solid carbon filled industrial product rather than C02.

So my question is, has anybody here really looked at this? Hydrocarbon combustion with carbon outputted in solid form? Is there research going on? Any input or leads would be appreciated, I am having a lot of fun researching this stuff.

Thanks!
Me
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DeSwiss Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Aug-14-11 03:56 AM
Response to Original message
1. Or....
Edited on Sun Aug-14-11 03:59 AM by DeSwiss
...how about a http://www.youtube.com/watch?v=VeE9ui7xvTU">aluminum/sodium hydroxide fueled car?


- You can stop and get a six-pack and your fuel (the cans) at the same time.....
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eppur_se_muova Donating Member (1000+ posts) Send PM | Profile | Ignore Tue Aug-16-11 04:48 PM
Response to Reply #1
8. The aluminum is just fuel produced by consuming LARGE amounts of electricity.
And NaOH is produced mostly by electrolysis as well.

Basically, you've found a way of shipping electricity from the power plant to your car. And all the Al2O3 needs to be recycled, or the process becomes fantastically expensive. Aluminum is cheap *ONLY* because ~90% of the metal is recycled.

What you have here is just another fuel cell, but one with notable disadvantages.
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HysteryDiagnosis Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Aug-14-11 05:51 AM
Response to Original message
2. Or how about some clean fuel?
www.rentechinc.com



Rentech can use a wide variety of carbon-bearing feedstocks including biomass, crop residue, natural gas, coal and petroleum coke to produce ultra-clean synthetic fuels and electric power.

Together with gasification and upgrading technology, the Rentech Process produces ultra-clean synthetic jet fuel branded under the RenJet name and ultra-clean synthetic diesel fuel branded under RenDiesel. The fuels produced from our process provide numerous environmental benefits during production and utilization.



The Rentech Process can produce fuels that are cleaner burning than petroleum-derived fuels and are biodegradable and contain virtually no soot-producing aromatics. In addition, RenJet and RenDiesel surpass all worldwide standards for ultra low sulfur diesel and jet fuels including engine and emissions control systems expected to be put in place in the near future. Exhaust or tailpipe emissions from our fuels are also lower than those from petroleum-based products, ensuring a cleaner tomorrow.

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madokie Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Aug-14-11 07:02 AM
Response to Original message
3. I wish you'd thrown in a link or two
I'd like to read more on this
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napoleon_in_rags Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Aug-14-11 03:29 PM
Response to Reply #3
4. There's incredibly little out there, but here's what I was looking at.
Edited on Sun Aug-14-11 03:32 PM by napoleon_in_rags
The process I was reading about is called SOHIO ammoxidation
http://portal.acs.org/portal/acs/corg/content?_nfpb=true&_pageLabel=PP_ARTICLEMAIN&node_id=924&content_id=WPCP_007593&use_sec=true&sec_url_var=region1&__uuid=2d513279-8b8c-419f-99d0-0f02ccdf405a
Its exothermic:
A key innovation was the successful development of a fluidized bed catalyst to allow for removal of the heat produced by the ammoxidation reaction.
And the chemical equation is from wikipedia
CH3CH=CH2 + 3/2 O2 + NH3 → NCCH=CH2 + 3 H2O
http://en.wikipedia.org/wiki/Ammoxidation (No CO2 that equation)
The chemical in the output other than water is Acrylonitrile, which is later heated to make carbon fiber, so that stuff is where the carbon resides, not the atmosphere. http://en.wikipedia.org/wiki/Carbon_fiber

Anyway, none if it is that is any kind of solution in itself, but I thought there must be some FUNDAMENTAL law of nature that states that hydrocarbon oxidation (combustion of gasoline, propane, the rest) MUST produce CO2 into the atmosphere to be exothermic and turn a motor. This equation shows me a hint that this isn't the case. oxidation of hydrocarbons can produce heat, and SOLID CARBON PRODUCTS instead of CO2. But that's where the trail ends, I can't find out more. If I'm wrong I want to know why, or if there's research I want to read about it, because like I said its a total environmental holy grail.
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madokie Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Aug-14-11 09:40 PM
Response to Reply #4
5. Thank you I'll check 'm out
Its the thinking out of the box that makes most big discoveries and has been always. This is thinking out of the box, keep up the good work.
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napoleon_in_rags Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Aug-15-11 12:02 AM
Response to Reply #5
6. Thanks!
That was definitely one I wanted to throw out there...I don't have the background or access to the materials to play with it, but MAN imagine what an epic win it would be if somebody invented a process like that which could power a car, outputting carbon fiber. It burns gas, outputs no carbon, and craps the highly expensive material needed to make wind turbine blades out its rear? Damn! :)
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eppur_se_muova Donating Member (1000+ posts) Send PM | Profile | Ignore Tue Aug-16-11 04:41 PM
Response to Original message
7. More simply, methane (CH4) can be thermally decomposed to form carbon and H2 ...
Edited on Tue Aug-16-11 04:50 PM by eppur_se_muova
this is how high-purity graphite is produced. The question is whether the combustion of H2 can generate enough energy to balance the energy cost of CH4 decomposition. Since you are not burning the carbon, you are recovering only part of the energy available from the fuel. This would mean *more* hydrocarbon would have to be burned to provide the same amount of energy. Now, there are other possilities, but they all face another issue -- what are you going to do with all that leftover carbon? Only a small fraction of petroleum is used to make plastics and intermediate chemicals; the rest is burned for fuel. The raw materials needed for production of plastics etc. is much smaller than the amount needed for fuels. So even if you succeed in "partial combustion" of HC's to form carbon and H2O, you're going to do it at the cost of pumping *more* oil out of the ground, and having to find a use for all that carbon you've brought to the surface -- and whatever you do, don't let it catch fire!

In regard to your question, "has anybody here really looked at this" (or something similar), I think you can safely say that yes, some of us have thought about this. Basically, it doesn't do enough to shift usage away from fossil fuels, since it all depends on propene. If you're going to use biomass to generate the propene, then partial combustion is kind of unnecessary, since you've closed the loop in the carbon cycle.

on edit: hadn't read your reply to a reply to the OP when I wrote this:

PS: PAN can be thermally decomposed to form carbon fiber and NH3 -- which potentially can be recycled to make more acrylonitrile, and thus more carbon fiber. So the overall process is propene + O2 --> carbon fiber + H2O. Pretty neat, assuming high efficiency at each step, which probably doesn't happen, or else carbon fiber would be a bit cheaper.
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