Author Topic: ISRU breakthrough? Copper-Gold catalyst for CO2->Methane  (Read 2145 times)

Offline LegendCJS

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Just came across this article about a new nano-particle copper gold catalyst that reduces the energy requirements for conversion of CO2 to hydrocarbons. 

http://web.mit.edu/newsoffice/2012/hybrid-copper-gold-nanoparticles-convert-co2.html

You have to take this story with a grain of salt (pardon the pun) and ignore the ramblings of an obviously delusional reporter suggesting a potential application: (capturing CO2 at coal power plants and converting it into methane for More Power! please...) of the technology that violates a couple laws of thermodynamics (1st and 2nd)..

But
I'll tell you what got me thinking about applications to a Mars mission.  It all depends on the energy requirements (no numbers in the report sorry):

The example has an electrode coated with the catalyst immersed in water with CO2 bubbling through it creating methane, so the Hydrogen involved starts out bundled to Oxygen.  This makes me question if this technique can be as energy efficient as a technique that starts with unattached H2 + CO2, but it opens some new trade spaces:

If
The energy requirements are comparable with the traditional pure H2 methods, then this option solves the cryogenic storage of H2 in transit problem.  No boil-off worries if the H2 is kept as water, much more flexibility too: you can now use this water in your radiation shielding much more easily that using liquid H2, or anywhere else it is needed.

Also
Any local source of hydrogen (which is going to be water) will not need electrolysis before being used to make methane out of CO2.  That at least might save a lot of energy even if the first idea doesn't pan out.
« Last Edit: 04/11/2012 06:12 PM by LegendCJS »
Remember: if we want this whole space thing to work out we have to optimize for cost!

Offline 93143

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Re: ISRU breakthrough? Copper-Gold catalyst for CO2->Methane
« Reply #1 on: 04/11/2012 06:18 PM »
No boil-off worries if the H2 is kept as water, much more flexibility too: you can now use this water in your radiation shielding much more easily that using liquid H2, or anywhere else it is needed.

The transit habitat and the ISRU equipment are usually on different flights.  The idea is that the crew doesn't launch until they know they can get back.

Also, water is 45% of the final propellant mass (more if you run fuel-rich), whereas pure hydrogen is only 5%.

Trade space...

Offline mrmandias

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Re: ISRU breakthrough? Copper-Gold catalyst for CO2->Methane
« Reply #2 on: 04/11/2012 08:09 PM »
If
The energy requirements are comparable with the traditional pure H2 methods, then this option solves the cryogenic storage of H2 in transit problem.  No boil-off worries if the H2 is kept as water, much more flexibility too: you can now use this water in your radiation shielding much more easily that using liquid H2, or anywhere else it is needed.

Also
Any local source of hydrogen (which is going to be water) will not need electrolysis before being used to make methane out of CO2.  That at least might save a lot of energy even if the first idea doesn't pan out.

I bet there are tradespaces where this is attractive for ‘cryogenic storage’ even if the energey requirements are somewhat greater.

Online A_M_Swallow

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Re: ISRU breakthrough? Copper-Gold catalyst for CO2->Methane
« Reply #3 on: 04/11/2012 09:40 PM »
There is water in the form of ice on Mars.  A rover can pull a trailer full of ice from the mine to the ISRU equipment.

Offline LegendCJS

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Re: ISRU breakthrough? Copper-Gold catalyst for CO2->Methane
« Reply #4 on: 04/11/2012 11:55 PM »
No boil-off worries if the H2 is kept as water, much more flexibility too: you can now use this water in your radiation shielding much more easily that using liquid H2, or anywhere else it is needed.

The transit habitat and the ISRU equipment are usually on different flights.  The idea is that the crew doesn't launch until they know they can get back.

Also, water is 45% of the final propellant mass (more if you run fuel-rich), whereas pure hydrogen is only 5%.

Trade space...

A compromise then.  Move the H2 form earth to Mars as a cyro liquid, but once at Mars, if you aren't going to turn it into Methane right away for some unknown reason but want to keep it around and stable for possible later methane production, there is a possibility of converting the H2 to water by cracking O form CO2.  This situation might arise if some future architecture required overland transport of landed H2 to a centralized ISRU plant.

There is a lot of work on making catalyst for the 2xCO2 -> 2xCO + O2 process too which will reduce the energy requirements there as well. 

I realize Mars surface boil-off of cryo H2 isn't a problem for an ISRU plant because any plant would use the H2 boil-off as it's feedstock instead of venting it like must be done in space/ transit.
Remember: if we want this whole space thing to work out we have to optimize for cost!

Tags: ISRU  CO2  Methane