Sciencemadness Discussion Board - Fuel from atmospheric CO2

Fuel from atmospheric CO2

Ritter - 23-6-2008 at 09:22

A project that interests me is the variation on the classic Fischer-Tropsch reaction that catalytically converts atmospheric CO2 into methane, methanol or higher chain length hydrocarbons. There appears to be an extensive literature on this topic. Given the current energy situation & concerns about CO2 contributing to global warming, this project should interest a number of subscribers here.

This chemistry can be broken down into 2 modules:

1. Sequestration of atmospheric CO2.
2. Catalytic conversion (reduction) of the CO2 into fuel.

Regarding sequestration of CO2, rather than build & power a gas separation plant to remove it from the atmosphere, I think that pumping air into aqueous caustic soda to form aqueous sodium carbonate or bicarbonate might have a lot going for it. That could be the starting point for continuous operation, which is nearly always desirable from an economic POV.

Here is one recent paper's abstract on the catalytic conversion of aqueous sodium carbonate into methane. Note that they hypothesize sodium formate being an intermediate. Formate esters can be reduced to methanol.

Quote:

In the presence of Raney alloy, the direct reaction of alkali or alkali-earth metal carbonates with water resulted in reduction of the carbonates to give methane in high selectivity at a temperature near the critical point of water (∼ 380°C). Raney Ni showed an efficient activity to promote the methanation. On the contrary, Raney Fe did not cause the methanation, but the addition of catalytic amount of a carbon-supported ruthenium (Ru/C) to the Raney Fe brought about a highly selective reduction of the carbonates to methane. The reaction was also controlled by the reaction temperatures, i.e., the selectivity and yield of methane increased with increasing temperature suppressing the formation of metal formate. One characteristic in the present reaction is a rapid formation of a considerable amount of metal formate at an initial stage. It is proposed that the formation of methane from metal carbonate occurs via the formation of metal formate and its subsequent hydrogenation by nascent hydrogen which is produced from water by action of Raney alloy. The apparent activation energy for the methanation of Na2CO3 on Raney Fe-Ru/C mixed catalyst was estimated to be 14 kcal mol-1.

Revue / Journal Title
Journal of molecular catalysis. A, Chemical ISSN 1381-1169
Source
1999, vol. 145, no1-2, pp. 159-167 (26 ref.)

[Edited on 23-6-2008 by Ritter]

Ritter - 23-6-2008 at 09:50

Here is another interesting report on similar chemistry:

Quote:

Originally published in Science Express on 1 April 2004
Science 14 May 2004:
Vol. 304. no. 5673, pp. 1002 - 1005
DOI: 10.1126/science.1096033

Reports

Hydrocarbons in Hydrothermal Vent Fluids: The Role of Chromium-Bearing Catalysts

Dionysis I. Foustoukos* and William E. Seyfried, Jr.

Fischer-Tropsch type (FTT) synthesis has long been proposed to account for the existence of hydrocarbons in hydrothermal fluids. We show that iron- and chromium-bearing minerals catalyze the abiotic formation of hydrocarbons. In addition to production of methane (CH4aq), we report abiotic generation of ethane (C2H6aq) and propane (C3H8aq) by mineral-catalyzed hydrothermal reactions at 390°Cand 400 bars. Results suggest that the chromium component in ultramafic rocks could be an important factor for FTT synthesis during water-rock interaction in mid-ocean ridge hydrothermal systems. This in turn could help to support microbial communities now recognized in the subsurface at deep-sea vents.

Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455, USA.

* To whom correspondence should be addressed. E-mail: fous0009@umn.edu

Ritter - 23-6-2008 at 09:56

Here is a comprehensive review article on the electrochemical reduction of CO2, carbonate & bicarbonate to obtain methane, higher hydrocarbons, formic acid, methanol, etc.

http://www.uctm.edu/journal/j2007-4/1_Jitaru_333-344.pdf

Ritter - 23-6-2008 at 10:12

Here is another report of abiogenic CH4 production from bicarbonate ion under hydrothermal vent conditions:

Quote:

Science 13 August 1999:
Vol. 285. no. 5430, pp. 1055 - 1057
DOI: 10.1126/science.285.5430.1055

Reports

Abiogenic Methane Formation and Isotopic Fractionation Under Hydrothermal Conditions

Juske Horita, 1* Michael E. Berndt 2

Recently, methane (CH4) of possible abiogenic origin has been reported from many localities within Earth's crust. However, little is known about the mechanisms of abiogenic methane formation, or about isotopic fractionation during such processes. Here, a hydrothermally formed nickel-iron alloy was shown to catalyze the otherwise prohibitively slow formation of abiogenic CH4 from dissolved bicarbonate (HCO3) under hydrothermal conditions. Isotopic fractionation by the catalyst resulted in 13C values of the CH4 formed that are as low as those typically observed for microbial methane, with similarly high CH4/(C2H6 + C3H8) ratios. These results, combined with the increasing recognition of nickel-iron alloy occurrence in oceanic crusts, suggest that abiogenic methane may be more widespread than previously thought.

1 Chemical and Analytical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
2 Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455, USA.
* To whom correspondence should be addressed. E-mail: horitaj@ornl.gov

Ritter - 23-6-2008 at 10:12

Here is another report of abiogenic CH4 production from bicarbonate ion under hydrothermal vent conditions:

Quote:

Klute - 23-6-2008 at 10:24

Very interesting topic indeed. I wonder if copper catalysts can effect that kind of reduction, and how re-useable the catalyst employed would be.
Adapting a small scale setup doesn't seem to a easy thing, especially if pressure is required for the reduction.

BTW, please use the edit function to avoid multiple posts like this....

Ritter - 23-6-2008 at 10:54

Quote:

Originally posted by Klute
Very interesting topic indeed. I wonder if copper catalysts can effect that kind of reduction, and how re-useable the catalyst employed would be.
Adapting a small scale setup doesn't seem to a easy thing, especially if pressure is required for the reduction.

A small-scale pilot unit could be built of coiled thick-walled metal tubing set inside a heat-resistant structure made of something like fire brick. I think standard gauges could be used to monitor pressure & I don't think thermocouples with digital readouts are very expensive. You would need to cool & then compress the output gas & store it in standard propane tanks such as are used to fuel gas grills. Your input stream of aqueous carbonate or bicarbonate solution would also have to be pumped to get to the needed pressures, which I think are in the range of 400 bar.

Of course you don't get something for nothing. You are hydrogenating the CO2 or bicarbonate or carbonate ions, so you need a source of hydrogen (water is preferred I think). You are also adding a tremendous amount of energy, which would be one of your major cost elements. But as the cost of fuels keeps rising, at some point this kind of 'do it yourself' CO2 recycling could become economically attractive.

As far as catalysts are concerned, they seem to be restricted to the transition metals, so Cu might work.

One other point: if your target is methane, you would have to be careful not to vent this to the atmosphere as it has many times the potency of CO2 in terms of a greenhouse gas.

[Edited on 23-6-2008 by Ritter]

[Edited on 23-6-2008 by Ritter]

Ritter - 23-6-2008 at 10:59

Here is a recent U.S. patent to a major university that claims the use of dehydrogenase enzymes coupled to spinach chloroplasts for NADH cofactor regeneration. CO2 goes in & methanol comes out in (claimed) high yield at room temperature & standard pressure:

http://tinyurl.com/4tb28m

Ritter - 23-6-2008 at 13:24

Quote:

Journal of Photochemistry and Photobiology A: Chemistry
Volume 182, Issue 3, 10 September 2006, Pages 306-309
Proceedings of 7th AIST International Symposium on Photoreaction Control and Photofunctional Materials

Half-sandwich complexes with dihydroxy polypyridine: Water-soluble, highly efficient catalysts for hydrogenation of bicarbonate attributable to electron-donating ability of oxyanion on catalyst ligand

Studies in Surface Science and Catalysis, Volume 153, 2004, Pages 263-266

Yuichiro Himeda, Nobuko Onozawa-Komatsuzaki, Hideki Sugihara, Hironori Arakawa, Kazuyuki Kasuga

Abstract
Half-sandwich Ru(II), Ir(III), and Rh(III) complexes with 4,7-dihydroxy-1,10- phenanthroline or 4,4′-dihydroxy-2,2′-bipyridine are highly efficient catalysts for hydrogenation of bicarbonate in alkaline aqueous solution without an amine additive. The generation of an oxyanion by deprotonation of the hydroxy substituents on the catalyst ligand caused a dramatic enhancement of catalytic activity due to its strong electron-donating ability of the oxyanionas well as imparting water solubility. Turnover frequencies (TOF) up to 42,000 h−1 and turnover numbers (TON) up to 222,000 have been obtained by using iridium catalysts under 6 MPa at 120 °C. The production of formate (TOF = 3.5 h−1) was observed even under ambient conditions (0.1 MPa, 30 °C).

roamingnome - 23-6-2008 at 18:24

Quote:

so you need a source of hydrogen

http://sciencelinks.jp/j-east/article/200415/000020041504A04...

...Pure hydrogen was formed by the reaction between biomass and NaOH at > 473 K in the absence of water vapor as well...

theres your hydrogen, but you need lots of economical NaOH

Is recycleing Na2CO3 back to NaOH tough?

stygian - 23-6-2008 at 19:04

Not too long ago I stumbled across a few articles relevant to this.

Ultrasonics Sonochemistry
Volume 5, Issue 2, June 1998, Pages 73-77

Involves sonication of CO2 solutions, producing CO, H2, and trace O2.

Another referred to bicarbonate reduction (to H2 and/or formaldehyde, depending on conditions) by iron salts under UV radiation.

They could be worth looking into.

edit: heres the latter article I mentioned: http://www.jstor.org/pss/32422

[Edited on by stygian]

not_important - 23-6-2008 at 19:12

Quote:

Is recycleing Na2CO3 back to NaOH tough?

Well, yes and no.

Na2CO3 (aq) + CaO is the old way of making lye. The CaO is made from CaCO3 by eating, which dumps the CO2 right back in the atmosphere. There are several other ways, all of which have the problem of cranking out CO2 and taking a fair amount of energy.

If you want to convert CO2 to more reduced forms, it's best not to start with the 380 ppm in the atmosphere, but rather to go for concentrated sources from big producers such as power plants.

Note that plants, which been in the CO2 fixing business for about a billion years, generally don't do much better than converting 1% of their energy input into fixed CO2 (mostly as carbohydrates). There's serious problems with the lifespan of synthetic systems, sensitivity to poisoning, and so on. Non-trival work remains to be done.

Ritter - 24-6-2008 at 09:56

Quote:

Originally posted by not_important

Quote:

If you want to convert CO2 to more reduced forms, it's best not to start with the 380 ppm in the atmosphere, but rather to go for concentrated sources from big producers such as power plants.

The classic Fischer-Tropsch process:

1. H2O (superheated steam) + C (powdered coal) > CO + H2
(synthesis gas, or syngas)

2. CO + H2 > Hydrocarbons + CO2

has not been implemented on a large scale yet in this country because the waste CO2 is vented to the atmosphere, adding to the greenhouse problem. Using the CO2 conversion options discussed above you could eliminate that waste problem with a 2-stage F-T plant.

FWIW, the U.S. has coal reserves that rival Saudi Arabia's oil reserves. And F-T technology is available off-the-shelf. You could build F-T plants near the coal mines.

The Germans ran WWII on F-T fuel and the South Africans are independent of imported oil because of their Sasol F-T initiative. And the U.S. Air Force is going F-T for avgas.

Conveniently, the usual output of a F-T plant is primarily linear hydrocarbons that are more suited for avgas & diesel applications, just what is needed for the trains, planes & trucks. I believe diesels are significantly more efficient than gasoline also.

12AX7 - 24-6-2008 at 21:32

Quote:

Originally posted by roamingnome
Is recycleing Na2CO3 back to NaOH tough?

Think about it. The process turns CO3(2-) (or HCO3-) into CH3OH. Thus, NaOH is left in solution.

Tim

Ritter - 25-6-2008 at 07:50

Quote:

Think about it. The process turns CO3(2-) (or HCO3-) into CH3OH. Thus, NaOH is left in solution.

Tim

I believe that the only other thing that gets consumed in this reaction is some of the water, so the aqueous NaOH could be reused after adjusting the concentration.

Panache - 1-7-2008 at 06:10

Quote:

Originally posted by Ritter

Regarding sequestration of CO2, rather than build & power a gas separation plant to remove it from the atmosphere, I think that pumping air into aqueous caustic soda to form aqueous sodium carbonate or bicarbonate might have a lot going for it. That could be the starting point for continuous operation, which is nearly always desirable from an economic POV.

This process, when applied industrially is known as 'Spent Caustic Carbonation' and is in use. Plants originally adopted it because it was a fairly cheap method of dealing with caustic waste. A college's father had developed and patented a mobile version on a semi that could trounce around from plant to plant on a rostered basis, but he died of cancer before he managed to attract enough investment to build it. That was in the early nineties. I am sure that these days, for plants producing (and having to dispose of) caustic waste, this process is very high on their list of 'pieces of kit to buy before the Co2 footprint audit' list.

F2Chemist - 1-7-2008 at 14:05

Never will happen. The problem is the energy losses. It's an uphill battle the entire way. At BEST (which will never happen), we are talking 0% energy loss (i.e. the amount of energy in the product = the amount of energy it took to make the product).

This is why hydrogen is such a silly idea. People think that it's a great SOURCE of energy, but what it really is is a crappy way to STORE and TRANSPORT energy.

12AX7 - 1-7-2008 at 14:07

What, exactly, will never happen?

You should notice no one mentioned hydrogen.

Ritter - 2-7-2008 at 05:07

Quote:

Originally posted by 12AX7
What, exactly, will never happen?

You should notice no one mentioned hydrogen.

Hydrogen currently comes from petrochemical plants, which generate it as a result of cracking ethane & propane to ethylene & propylene. But the amounts of hydrogen required to make a significant impact on domestic hydrocarbon fuel consumption would be huge & most likely would have to come from electrolysis of water, which would require equally huge amounts of electric energy.

Beyond the basic economics of producing hydrogen, you would have to transport it & we currently have a bulk fuel transport infrastructure that is dedicated to hydrocarbon fuels. How are you going to transport hydrogen & do it safely?

The most significant problem with hydrogen comes at the consumer level. Forty-nine of the 50 states have filling stations designed for pump-it-yourself service. Just imagine the chaos as millions of untrained people try to fill their tanks with a pressurized & highly flammable gas! And a car with a tank of pressurized hydrogen becomes a fuel-air bomb just waiting for an accident to trigger it.

I still feel that the most feasible fuel source is F-T conversion of coal to diesel & avgas. The technology exists now. The Germans & the South Africans proved that it works. And our current distribution infrastructure would not have to be either enhanced or modified. The price of oil is getting close to where the economics of F-T fuel will be both competitive & a lot cheaper than an endless series of Middle Eastern wars fought for oil.

[Edited on 2-7-2008 by Ritter]

[Edited on 2-7-2008 by Ritter]

F2Chemist - 2-7-2008 at 08:39

Quote:

Originally posted by 12AX7
What, exactly, will never happen?

You should notice no one mentioned hydrogen.

Since the post was fuel from CO2, that may be what I was speaking of. Also, I was using hydrogen as a SIMILAR example.

Polverone - 2-7-2008 at 10:29

Quote:

Originally posted by Ritter
I still feel that the most feasible fuel source is F-T conversion of coal to diesel & avgas. The technology exists now. The Germans & the South Africans proved that it works. And our current distribution infrastructure would not have to be either enhanced or modified. The price of oil is getting close to where the economics of F-T fuel will be both competitive & a lot cheaper than an endless series of Middle Eastern wars fought for oil.

I think the amortized costs of production for F-T already make coal-to-liquids cheaper than imported crude for the US. There are at least two problems, though. The first is that building a new CTL plant, at least one like those Sasol uses, is extremely capital intensive. The second is that not everyone is confident that the current high and rising price of oil reflects a "fundamental" valuation. Some think that oil is currently experiencing a price bubble. It's very doubtful that oil would ever be as cheap again as it was in the late 1990s, but if the current price is speculation-driven it could drop 30-50 dollars a barrel even faster than it gained the last 30-50 dollars per barrel. Even if it's not speculation driven, an economic slowdown or recession could drop the price of oil due to decreased demand. The very high current price of crude oil is good news for purveyors of alternatives, but a stable price (even if somewhat lower than it is now) would be better yet. Even in an era of $140/barrel oil, a 7 billion dollar CTL plant needs some time to show a profit.

Governments and other large investors got burned on energy investments during the fuel crisis of the 1970s. By the late 1970s, early 1980s there had been a lot of R&D on crude oil alternatives and energy efficiency measures (oil shale, coal to liquids, solar heated buildings, MHD generators...) and a number of pilot scale programs. Then oil prices dropped in the mid 1980s and most of the fruits of investment became uncompetitive with business-as-usual. Investors may be more cautious this time around, even though there are strong signs that oil prices are not going to collapse again.

[Edited on 7-2-2008 by Polverone]

Ritter - 2-7-2008 at 11:10

Quote:

Originally posted by Polverone
I think the amortized costs of production for F-T already make coal-to-liquids cheaper than imported crude for the US. There are at least two problems, though. The first is that building a new CTL plant, at least one like those Sasol uses, is extremely capital intensive. The second is that not everyone is confident that the current high and rising price of oil reflects a "fundamental" valuation. Some think that oil is currently experiencing a price bubble. It's very doubtful that oil would ever be as cheap again as it was in the late 1990s, but if the current price is speculation-driven it could drop 30-50 dollars a barrel even faster than it gained the last 30-50 dollars per barrel. Even if it's not speculation driven, an economic slowdown or recession could drop the price of oil due to decreased demand. The very high current price of crude oil is good news for purveyors of alternatives, but a stable price (even if somewhat lower than it is now) would be better yet. Even in an era of $140/barrel oil, a 7 billion dollar CTL plant needs some time to show a profit.

Here is a somewhat dated cost analysis of building & operating a F-T plant: http://www.netl.doe.gov/publications/proceedings/97/97cl/cho.... Even taking inflation into consideration, actual cost is likely closer to a billion $ than to $7B.

My information is that the oil supply rate has peaked while the demand rate is increasing at over 2%/year, compounded. All the cheap oil has been consumed & what is left should be reserved for applications where there are no feasible alternative, such as petrochemical feedstocks for chemical raw materials that can be made in no other way.

The situation with oil is a serious matter involving national security. It is a similar situation to the situation the Germans faced in the World Wars, that South Africa faced with oil embargoes, and the situation that the U.S. found itself in when WWII started & supplies of natural rubber were cut off. A major effort in all these cases relieved the fuel & rubber shortages through the application of organic chemistry.

The true irony of the current situation is the fact that the major oil companies all led the research effort in the U.S. on F-T technology. Since they own most of the distribution infrastructure, tax credits to Big Oil should be tied to capital investment in F-T plants located near major coal producing areas.

In the near term, if the current trend in oil cost is not brought under control, I predict we will see 1973-style rationing, with the bulk of the oil products being shifted to the trains, trucks & planes in order to prop up our national transportation infrastructure.

Hopefully this country will soon lose its oil baron leadership & put someone with broad vision in their place.

Here is a typical F-T pilot plant:

[img]http://f9g.yahoofs.com/groups/g_17454011/.HomePage/__sr_/becf.jpg?grAgWbIBCSg8xts2[/img]

[Edited on 2-7-2008 by Ritter]

MagicJigPipe - 2-7-2008 at 12:27

Unfortunately, we need an "oil baron". Right now (or even within the next 20 years) if oil becomes too expensive/unavailable we are screwed. VERY screwed. What we need is someone who can be an "oil baron" while, at the same time, actively searching for other alternatives. I almost got ahead of myself there. What many people seem to have forgotten is that the president doesn't (or SHOULDn't anyway) have much control over those types of things. His main purpose is to enforce the laws and help in the "3-way" govt. process. I feel that sometimes we rely on him to be a dictator that can control directly what the nation spends its money on.

In some ways that would help. But we don't want that now do we?

I think the future is in fusion. Once we figure out how to get more energy out of it than we spend... Well, we'll have all the hydrogen we want. And once we have that setting up infrastructure for it will just be a minor issue (since we'll basically have "free" energy... yes I know it's not really "free").

You guys know what I mean... gotta go laksdhf;asdhf

F2Chemist - 2-7-2008 at 13:08

My money for the future is on hot dry rock geothermal energy. Basically it involves drilling a REALLY deep hole, pumping water down there and using the steam generated to power turbines. Problems with it right now are keeping the hole stable (we're talking 3-5 km holes).

If that doesn't work, maybe a global war/plague, elimating two thirds of the world population will.

Ritter - 2-7-2008 at 13:39

Quote:

Originally posted by MagicJigPipe
I think the future is in fusion. Once we figure out how to get more energy out of it than we spend... Well, we'll have all the hydrogen we want.

You can't run trains, planes & trucks on hydrogen, which is a nightmare to make, transport & handle safely at the consumer level in the kinds of quantities required. And fusion is 10+ years away...maybe.

Ritter - 2-7-2008 at 13:42

Quote:

Originally posted by F2Chemist
If that doesn't work, maybe a global war/plague, elimating two thirds of the world population will.

Not to worry. It will come in the not-so-distant future. Either we or the Israelis will start WWIII with Iran or there will be wars on the Indian subcontinent when the Himalayan glaciers finish receding & all their water goes away.

[Edited on 2-7-2008 by Ritter]

Ritter - 2-7-2008 at 13:48

Quote:

Originally posted by MagicJigPipe
Unfortunately, we need an "oil baron".

Unfortunately, the oil barons currently in charge have only one policy: more profits for their oil baron buddies in Houston. This country has no other energy policy. You can't run trains, planes & trucks on wind or solar or hydrogen.

JohnWW - 2-7-2008 at 13:54

Quote:

Originally posted by F2Chemist
My money for the future is on hot dry rock geothermal energy. Basically it involves drilling a REALLY deep hole, pumping water down there and using the steam generated to power turbines. Problems with it right now are keeping the hole stable (we're talking 3-5 km holes).

There is enough geothermal energy available in New Zealand, especially in the Bay of Plenty, central North Island volcanic plateau (which has the world's thinnest continental crust), and Northland, to power the whole country, if it could be so arranged. However, to develop it much beyond current and immediately planned utilization, involving mostly greater depths than hitherto tapped, a very heavy capital outlay would be required.

Polverone - 2-7-2008 at 14:31

Quote:

Originally posted by Ritter
Here is a somewhat dated cost analysis of building & operating a F-T plant: http://www.netl.doe.gov/publications/proceedings/97/97cl/cho.... Even taking inflation into consideration, actual cost is likely closer to a billion $ than to $7B.

That cost estimate is for a natural gas to liquids plant. Producing syngas is going to be a lot more complicated in a coal plant, I would think. I threw out the $7 billion number because I got that from a 2007 article about coal-based Sasol plants being constructed in China. "Typical" cost of a Sasol plant was said to be $5-$7 billion for a plant with 80,000 barrels/day output. With the weakening dollar, more expensive labor, and stricter US environmental regulations I'd expect the price of a US-located plant to be at or above the upper number given for the Chinese plants. EDIT: I notice also that the plant in the study you linked to was for a much smaller plant, with 8,820 barrels/day of liquid production.

I just saw an EIA report that indicates oil prices are almost certainly driven by fundamentals and will remain high for at least the next 5 years. My earlier comment about speculators possibly driving up the price of oil should be taken with an even larger grain of salt than I originally intended.

I recognize that the rising price of oil has a political dimension, but I ask that discussion here be confined to economics and technical issues. We have a general moratorium on political discussion because political discussion formerly led to many heated arguments that sucked up all the moderators' time.

[Edited on 7-2-2008 by Polverone]

MagicJigPipe - 2-7-2008 at 17:01

Quote:

Yes, you can. It's just not very practical. What I mean is, once you have some sort of cheap source of energy created other "forms" of energy storage is much easier. For example, one could use the hydrogen produced in other power plants... But, if we had no other option, it certainly wouldn't be impossible.

ShadowWarrior4444 - 2-7-2008 at 17:25

Quote:

Originally posted by MagicJigPipe

Quote:

Hydrogen is a hideously annoying form of energy storage, its gaseous, enjoys diffusing through metals, and is quite flammable. [Producing it via electrolysis is just *silly,* too.] The only viable form of hydrogen storage for a mass economy is hydrogen stored in a crystalline matrix, or as another solid compound. It could then be converted to a gas for transfer between such artifices.

I much prefer using nuclear and electrical power sources. A pebble-bed reactor (using U-238 encapsulated in graphite) fed into Silver-Zinc Matrix batteries will likely be the future.

Silver-Zinc Matrix batteries are not plagued by the memory effect, and pebble bed reactors are not capable of overloading, or having a criticality accident. Toshiba has even designed an in-home nuclear reactor, though I am not certain whether it uses the pebble bed technology.

Ancillary Notes:
http://gltrs.grc.nasa.gov/reports/2007/TM-2007-214806.pdf

[Edited on 7-2-2008 by ShadowWarrior4444]

12AX7 - 2-7-2008 at 17:36

Quote:

Originally posted by ShadowWarrior4444
Silver-Zinc Matrix batteries are not plagued by the memory effect

Neither are lithium ions, lead acids, NiMH, or NiCd really. Basically any rechargable technology known to man and used under average consumer circumstances. Memory effect is the rechargable boogeyman and, I'm sorry to inform you, has spooked you like a six year old!

Memory effect per se is an artifact of NiCd chemistry and is only produced under very specific conditions, namely, clocklike cycling of charge. This is hardly a concern outside of satellites (which use lighter lithium technology these days anyway).

Thread drift marches on...

Tim

ShadowWarrior4444 - 2-7-2008 at 19:43

Quote:

Originally posted by 12AX7

Quote:

Originally posted by ShadowWarrior4444
Silver-Zinc Matrix batteries are not plagued by the memory effect

All rechargeable batteries are subject to the memory effect in varying degrees, repeated charging and discharging of Lead-acid batteries for example degrades the PbO2 plate, causing it slough off leading to voltage depletion. Even Ni-MH batteries are effected under the very common condition of recharging the cell before it is completely discharged (http://www.duracell.com/oem/Pdf/others/nimh_5.pdf) which would certainly be the case should one use them to store energy from a nuclear energy source.

Li-Ion would be horrible choices for such an application as the propensity for thermal runaway wouldn’t be very nice.

I noted Silver-Zinc Matrix batteries because they store 50% more energy than Li, are a wee bit lighter, and never experience voltage depression or thermal runaway under conditions.

P.S. "Spooked like a six-year-old" is not an accurate description of thoughtful long-term planning.

Ancillary: As the thread has seemed to have swerved off-topic, I'll attempt to recall it with this--

The http://en.wikipedia.org/wiki/Miller-Urey_experiment is very similar to what is being discussed here. In the article it also mentions that "Wilde only used voltages up to 600 V on a binary mixture of carbon dioxide and water in a flow system. He only observed small amounts of carbon dioxide reduction to carbon monoxide and no other significant reduction products or newly formed carbon compounds."

That aside, higher voltages may be effective at reducing CO2 to a more useful compound--perhaps an atmosphere of CO2 and NH3 electrolyzed at high voltage may form complex organic molecules that at the very least could serve as the feedstock for a biologically-based energy production system.

I have also heard that electrolysis of Mars' atmosphere is being considered as a long term terraforming project.

[Edited on 7-3-2008 by ShadowWarrior4444]

nodrog19 - 2-7-2008 at 20:00

CO2--->C+O2 via electrolysis of the liquid phase might work.
its going to be cold so Sterling Heat engines could power the electrolysis

Nicodem - 3-7-2008 at 04:07

Quote:

Originally posted by nodrog19
CO2--->C+O2 via electrolysis of the liquid phase might work.

CO<sub>2</sub> does not dissociate neither is it a ionic compound, so you can not electrolyze it.
(http://en.wikipedia.org/wiki/Electrolysis)

JohnWW - 3-7-2008 at 04:13

I think Nodrog19 is confusing CO2 with ionic carbonates, like Na2CO3. Electrolysis of an aqueous solution of that would result in either a solution of NaOH with CO2 being given off, or of peroxycarbonate, which I have read somewhere is blue in color, depending on the conditions.

froot - 3-7-2008 at 06:30

The days of gasoline and diesel will end at some stage. The coal and oil reserves may be far from depleted but the end of the supply will eventually come. It may be that political/environmental/cost issues will accelerate this day towards us but the day is coming.
From a chemistry point of view these archaic fuels are certainly messy, consisting of a coctail of hydrocarbons, phenols and other crap around which man has adapted his machines to drink. We all know that pure fuels burn cleaner, for example compare that of methanol with diesel. The future lies in more precise fuels, whatever they may be because only with this kind of selectivity can we start optimising from an efficiency and environmental point of view.
I think it is always a good idea to have a back door, an alternative to the run of the mill source of energy, and the CO2 method presented here is just another way to convert other energy into useful energy, be it ineffiecient, it is just another option made available to us as we explore the gauntlet of organic chemistry. I believe there is big treasure hidden down there somewhere that will drive the final nail in the dirty fuels coffin.

Here is a cost comparason:
Methanol in my currency is at the moment R3.99 a liter, while 500ppm diesel is R11.80 a liter, that's a third of the price! The funny thing is that diesel is less refined than gasoline and it's more expensive here, go figure.
Methanol may not have a high BTU but it burns cleaner and the costs outweigh its disadvantages. Both methanol and diesel are toxic so that kind of cancels out. I would really like to explore converting to methanol.

F2Chemist - 3-7-2008 at 07:07

Methanol is also quite corrosive to the typical infrastructure we have in place. If you are looking for a great read on why methanol didn't take off in the 80's (and some striking similarities it has when compared to today's push for a hydrogen economy), I highly suggest you pick up "Beyond Oil and Gas: The Methanol Economy" by Dr. Prakash.

Ritter - 3-7-2008 at 09:55

Quote:

Originally posted by ShadowWarrior4444

I much prefer using nuclear and electrical power sources. A pebble-bed reactor (using U-238 encapsulated in graphite)

And where are you going to store the spent nuclear fuel?

h2o2guru - 3-7-2008 at 17:06

To get a little more on topic here, Something I've been doing a little research on , no make that A LOT of research on for the past 4 years is

CO2 to Formic acid !!!!!

The electrochemical manufacture is ~99% efficient. its a pretty old technology, some of the patents are pretty old. (Faradically efficient)

Formic acid can be further converted to other chemicals like methanol and others.

Formic acid can be passed over catalysts to break down into CO2 + H2 , a great way to store hydrogen!

The only bad thing about it is you have to use a expensive form of energy like electricity.

So far I've been concentrating on Co2 concentration from the atmosphere. Zeolites work pretty well, I've just have valve problems.

Anyone know any interesting Formic acid chemistry ?

ShadowWarrior4444 - 3-7-2008 at 18:34

Quote:

Originally posted by F2Chemist
Methanol is also quite corrosive to the typical infrastructure we have in place. If you are looking for a great read on why methanol didn't take off in the 80's (and some striking similarities it has when compared to today's push for a hydrogen economy), I highly suggest you pick up "Beyond Oil and Gas: The Methanol Economy" by Dr. Prakash.

This is quite true, alcohol fuels are most definitely not the future. They have one quite large disadvantage, especially methanol. They are miscible with water, and have the tendency to do so whenever possible.

It is also biologically based, which I tend to dislike given that humanity's future is most likely not going to be confined to Earth. Inorganic energy sources such as fissionable materials and fusion of light elements must inevitably be our direct power source. It is that way now, infact--it is just that plants serve as the 'middle-man' for us.

Developing fusion and fission power sources will remove our dependence on the sun. And naturally, electrical devices serve as the best modes for storage and use of such energy. The elements required to construct and power nuclear/electrical devices are found readily all over the universe.

Quote:

CO2 does not dissociate neither is it a ionic compound, so you can not electrolyze it.

Lies!

http://ares.jsc.nasa.gov/HumanExplore/Exploration/EXLibrary/...
http://www.niac.usra.edu/files/library/meetings/annual/jun00...

Ancillary: Lasing the ionosphere of Mars and other suitable planets is also being researched by the US Airforce.

[Edited on 7-3-2008 by ShadowWarrior4444]

JohnWW - 3-7-2008 at 19:13

Quote:

Originally posted by Ritter

Quote:

Originally posted by ShadowWarrior4444
I much prefer using nuclear and electrical power sources. A pebble-bed reactor (using U-238 encapsulated in graphite)

And where are you going to store the spent nuclear fuel?

The spent fuel rods, originally consisting of uranium enriched in U-235 at the expense of U-238, consist of a mixture of the fission products of U-235 (Ba, Cs, Sr, and I being common amongst them, and including many radioactive isotopes), Pu-239 produced from absorption of liberated neutrons by U-238, and a small amount of unutilized U-238. The Pu-239, being fissionable, can be extracted, and used in new fuel rods to generate power (or in bombs), of smaller size than the U ones because of its lesser critical mass.

[Edited on 5-7-08 by JohnWW]

not_important - 3-7-2008 at 19:29

To continue on that, for standard civilian fission reactors approximately 95% of the spent fuel is fissionables, the worst of the remainder is isotopes with half lives of less than 50 years, many with much shorter than that.

not_important - 3-7-2008 at 20:12

Quote:

Originally posted by h2o2guru...

CO2 to Formic acid !!!!!

The electrochemical manufacture is ~99% efficient. its a pretty old technology, some of the patents are pretty old. (Faradically efficient)

Formic acid can be further converted to other chemicals like methanol and others.

Formic acid can be passed over catalysts to break down into CO2 + H2 , a great way to store hydrogen!

...

Instead, just don't put the CO2 there in the first place.

HCO2H 46 g/mol, d 1,22 = 26,5 mol/liter = 26,5 mol H2
NH3 17 g/mol, d(l) 0,69 = 40,5 mol/l = 60,88 mol H2
Mg(NH3)6Cl2 stores NH3 at the same volumetric density as liquid ammonia with a vapour pressure of NH3 about the same as 1/2 percent aqueous ammonia. Both liquid NH3 and the amine complex store about 1,5 times as much energy per liter as liquid H2.

Haber–Bosch can use electrolytic hydrogen, or NH3 can be made by newer direct solid state electro-syntheses from waer and nitrogen.

http://www.energy.iastate.edu/Renewable/ammonia/ammonia/2007...

http://www.ecn.nl/docs/library/report/2005/rx05085.pdf

http://www.energy.iastate.edu/Renewable/ammonia/ammonia/2006...

http://www.electricauto.com/_pdfs/Portland%20Paper%20B.pdf

http://www.energy.iastate.edu/Renewable/ammonia/ammonia/2007...

http://www.energy.iastate.edu/Renewable/ammonia/ammonia/2007...

http://www.energy.iastate.edu/Renewable/ammonia/ammonia/2007...

http://www.ent.ohiou.edu/~kremer/NH3Car/VehicleOverview.pdf

http://www.sandia.gov/surface_science/pjf/On_NH3_roles_in_H2...

http://www.energy.iastate.edu/Renewable/ammonia/ammonia/2005...

12AX7 - 3-7-2008 at 21:08

Quote:

Originally posted by JohnWW
The spent fuel rods, originally consisting of uranium enriched in U-235 at the expense of U-238, consist of a mixture of the fission products of U-235 (Ba, Cs, Sr, and I being common amongst them, and including many radioactive isotopes), Pu-239

He was talking about pebble bed reactors (snipped, but you even quoted it), but that doesn't matter. Besides that, I wanted to point out that commercial reactors are NOT very useful for nuclear proliferation, because the 239Pu formed is rather quickly bumped up to higher isotopes, up to 244Pu, which is completely unsuitable for weapons.

Some of the waste products are poisons (neutron absorbers), reducing yield and making the fuel useless. Some of the products are valuable (radioactive rhodium isotopes have a maximum half-life of only a few years, so reprocessed wastes can be released on the market after cooling off only a few decades), and all the actinides can be sent back to be burned some more (including U238, if used in a breeder reactor). But the cost of reprocessing is quite high and overall energy yields aren't very big, only a few times, so it's a lot less hassle to dump the stuff in a hole. Which is a fine environmental decision (despite what many make of it).

But you know as well as I do this has even less to do with CO2 than this thread needs.

Tim

Polverone - 3-7-2008 at 21:49

Quote:

Originally posted by 12AX7
Besides that, I wanted to point out that commercial reactors are NOT very useful for nuclear proliferation, because the 239Pu formed is rather quickly bumped up to higher isotopes, up to 244Pu, which is completely unsuitable for weapons.

That's not really true. 1, a commercial reactor can be used with low fuel burnup to produce more weapons-suitable plutonium (assuming there's no IAEA or other controls to prevent excessively frequent refueling). 2, the US already successfully tested a bomb made from reactor grade plutonium. Bombs made from plutonium recovered from higher burnup fuel will have hotter pits that emit more radiation, and will be more prone to predetonation, but the greater engineering difficulty in achieving reliable yields still seems like a tradeoff that would-be nuclear powers would accept if it made obtaining fissile material easier. I don't think there's a concern about terrorists building weapons from stolen fuel, but weapons-seeking nations might reprocess spent fuel for weapons if it isn't monitored.

12AX7 - 3-7-2008 at 22:31

Interesting, I hadn't heard of any "reactor grade" weapons.

"Excessively frequent refueling" is a hassle, so presumably wouldn't be a concern for a reactor that's just making power. Of course, if nonproliferation is a concern in whatever country, it may not be making just power...

Tim

Ritter - 4-7-2008 at 06:09

Quote:

Originally posted by JohnWW

Quote:

Originally posted by Ritter

Quote:

Originally posted by ShadowWarrior4444
I much prefer using nuclear and electrical power sources. A pebble-bed reactor (using U-238 encapsulated in graphite)

And where are you going to store the spent nuclear fuel?

And why are they not doing that now, as they did for making Pu at Hanford? All spent fuel rods are stored on-site at nuclear power plants in water pools. Yucca Mtn involves moving it all via rail & truck through Las Vegas, which will likely never fly.

not_important - 4-7-2008 at 06:30

The US does not recycle spent fuel based on a policy similar to those that prevent people from hand carrying expensive frequent-does prescription medicine onto airplanes - as a protection against terrorism. The US claims the no-reprocessing policy is to prevent the proliferation of nuclear weapons, but this is obviously not true given the US policies towards India, Pakistan, Israel, and continuing to work to secure former Soviet nuclear materials (see V Plame).

Nicodem - 5-7-2008 at 04:19

To those who are wondering where their posts disappeared:

There is a moratorium on political discussions on the ScienceMadness forum and I'm sure all except of the newcomers are aware of this. So don't start again with completely off topic discussions related to power and control, especially if based on ideological argumentation. They will be promptly removed again. If your urge gets unstoppable rather use one of the so many political forums out there.
Stick to science and thread topics!