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Reaction of carbon dioxide and methane

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johnpool:
It is expected that as a result of climate change, the permafrost in Siberia will thaw. This will release large amounts of methane into the atmosphere. Methane is a strong greenhouse gas, even stronger than carbon dioxide.
 
Question: is it theoretically possible to let methane and carbon dioxide react so that pure carbon and water are formed? (CO2+CH4 -> 2C+2H2O). If this could be done on a large scale, it could help solve the greenhouse gas problem.

If this is a stupid proposal/question (which is probably the case): I'm not a chemist, just a computer scientist from the Netherlands.

Regards, John Pool

Borek:
To "let" them react? No.

To use a lot of energy to produce carbon and water from these gases? Yes.

But when we have plenty of cheap energy we can just stop burning fuels and stop CO2 emissions. Which may (or may not, if we are beyond some tipping point) stop the climate changes.

Corribus:
Just because you can write a reaction equation does not mean it is thermodynamically or kinetically favorable. Neither methane nor carbon dioxide are particularly reactive gasses. A quick analysis by heats of formation and standard entropies yields an estimated ΔH° and ΔS° under standard conditions to be on the order of -15 kJ/mol and -13 J/molK respectively (for the products being solid carbon and water vapor). This would imply a reaction that is thermodynamically spontaneous at room temperature (ΔG° ~ -11 kJ/mol) but gets progressively less so at higher temperatures due to an unfavorable entropy contribution. Nevertheless, we don't see solid carbon falling out the sky everywhere so it would seem to suggest some kinetic barrier, possibly a high energy intermediate. Maybe one would come up with some kind of selective catalyst to increase the reaction rate. But then one must contend with the fact that water vapor is also a potent greenhouse gas.

Enthalpy:
Such spontaneous reactions stop at CO.

When the conditions push for it, you get a mix of H2, CO and more exotic things. C forms only if oxygen is too scarce for CO, then H2O is much more rare.

In fact, opposite reactions exist and serve to produce gaseous and liquid fuels from coal (...which isn't quite carbon) and water.

Other difficulty: capturing anything from the atmosphere. Not only are the amounts of CO2 (and CH4) colossal, one must treat air amounts even much bigger.

billnotgatez:

--- Quote from: Corribus on November 28, 2022, 12:30:55 PM ---... Maybe one would come up with some kind of selective catalyst to increase the reaction rate. But then one must contend with the fact that water vapor is also a potent greenhouse gas.

--- End quote ---

green plants and sunshine?

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