Talk:Sabatier reaction

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This is an important page and needs to be expanded upon. Currently, the Sabatier Reaction seems to be only used in discussions of how to create rocket fuel from the lunar surface or the martian surface. However, this reaction is potentially interesting for discussions of a hydrogen economy. In particular, methane would appear to be an existing method for transporting hydrogen; it transports 25% hydrogen by weight (compare to carbon nanotubes, glass beads, or metal hydrides); it has better volume properties than pure hydrogen; and there exist fuel cells that will directly consume methane.

Discussions of cost information for synthesizing methane from water and carbon dioxide are hard to come by. Other discussions of how practical it might be to expand the existing methane economy for transportation purposes while recycling carbon dioxide would be interesting. —Preceding unsigned comment added by (talkcontribs) 15:56, 18 March 2005

Currently the reaction goes in the other direction. Most hydrogen is produced from methane. To make the Sabatier reaction go, it requires much cheaper hydrogen, or much more expensive fossil fuels. pstudier 00:40, 2005 Jun 10 (UTC)
The most important thing is the energy balance, even if the prices of hidrogen generation or fuel don't move. But this is a hard work, and the way to do the study can change the results. So, I think that a comparison of a few works is needed. --Proximo.xv 12:07, 12 December 2006 (UTC)


I plan on including more details of the reaction process and how a reactor would work (in a new section entitled "Process"), however I'm not a chemist and finding detailed information on this that I can understand is apparently not very easy. So far I've got a ceramic (alumina) foam catalyst cooking at around 400-700 degrees F; the reaction is exothermic meaning the exhaust (methane and steam) comes out hotter than the intake. Apparently the reaction occurs spontaneously in these conditions, so a pump to keep the CO2 and 4H2 moving is all that is required. Using a ruthenium catalyst can reduce the starting temperature significantly, nickel has a higher starting temperature. Below are some links that have some more information on the process:

There are also numerous advantages to manufactured methane over fossil fuels and I believe this should be explained in the article as well - including carbon neutrality, existing pipeline infrastructure, ease of compression and storage etc; however finding people who want to burn methane (instead of going backwards and turning it into hydrogen) to cite as references is also a pain.---Puff (talk) 16:13, 30 July 2009 (UTC)

An exothermic reaction[edit]

I read t5hat this reaction is an exothermic reaction.Agre22 (talk) 14:40, 17 September 2009 (UTC)agre22 ~ I do believe that an exothermic reaction is described as a positive delta H, the reaction specified has a negitive delta H (ie the reaction 'absorbs' energy, hench when you burn methane CH4 with oxygen O2 it realeases heat [ie its exothermic])

Rocket propellant on Mars surface[edit]

Why would it be that important to make Methane on Mars surface when we now know there are vast quantities of water available there, from which the more efficient rocket propelant Hydrogen+Oxygen could be easily produced ?

Almipa (talk) 15:17, 16 April 2010 (UTC)

Who's to say it's more efficient? It's high performance but that isn't the most important thing on mars. Practicality is, and Hydrogen is hard to store (extremely low temps), and the water needed would have to be mined from martian soil. If you want to fuel your return ship before you get to mars (highly recommended!) then you will need to do this roboticly which is going to be fraught with problems. Not impossible, but there's easier ways. If you simply bring your hydrogen from earth, which doesn't weigh much, then all you need to do is run an air compressor and power up the synthesis plant when you land. You use up the small amount of hydrogen right away so you only have to endure boil-off during the 6 month trip out to mars. You don't need to store a much larger volume of H2 for years, in very large tanks attached to your return ship etc. A methane powered mission would be cheaper and safer in this way. Later, when there is a human presence, a base, we would certainly be mining for water and then it may make sense to use H2 as fuel. But then again, we may stick to methane because it still very easy to store at martian temps and still a very good performing fuel. (talk) 22:54, 18 May 2010 (UTC)


I am confused by the line "The stoichiometric ratio of oxidizer and fuel is 3.5:1, for an oxygen:methane engine, however one pass through the Sabatier reactor produces a ratio of only 2:1." Where does the 3.5:1 figure come from? For diatomic oxygen and methane reacting to carbon dioxide and water, the ratio is 2:1; with monatomic oxygen, the ratio is 4:1. Other values (such as the 2:1 figure in this line) seem to refer to the monatomic case. If this 3.5:1 ratio is accurate for some reaction, it would be helpful to show the reaction it describes or provide a link to another article which describes it. It might also be useful to note in the line above that the oxygen produced from a "pass through the Sabatier reactor" assumes electrolysis of the water. -- (talk) 17:21, 1 November 2010 (UTC)

I believe this is still a correct criticism, since one CH4 combusts to one CO2 and two H2O with the addition of 2 O2... rewriting that, it is
CH4 + 2 (O2) -> CO2 + 2 (H2O)
or a stoichiometric ratio of 2:1 ... now it is true that engines are often run fuel rich or oxidizer rich for various reasons. If expressed using O rather than O2, a 3.5:1 ratio would be somewhat fuel rich but not outside the realm of possibility (oxidizer rich tends to be corrosive, which is bad for reusable engines). But that's not what it says. Correction seems warranted. ++Lar: t/c 20:36, 9 April 2013 (UTC)

"Where does the 3.5:1 come from?" Stoichiometricaly, methane and oxygen burn in a 2:1 ratio. (Or a Oxidizer to fuel ratio of 4:1 by mass). But rocket propellants seldom burn Stoichiometricaly, because a little unburned fuel often improves the characteristics of the exhaust. For instance the RD-185 has a O/F ratio of 3.4, and the raptor engine 3.8 . Now, the 3.5:1 is missing in the article. The question is if this is a notable detail. (talk) 22:21, 18 October 2015 (UTC)

I read the Stoichiometry article and it seems to me that we could clear this up by explaining that 4:1 is a mass ratio and 2:1 is a mole ratio.... not sure of the best wording. Anon, maybe you could take a crack at it? (PS I do agree that clarifying that these engines tend to burn fuel rich is helpful and I think that it would be a good clarification to add...) ++Lar: t/c 15:28, 21 October 2015 (UTC)
HOWEVER, the 3.5:1 ratio has been removed from the article it appears, so this all may be moot. ++Lar: t/c 15:36, 21 October 2015 (UTC)