Anyone know anything about catalysts?

This is probably one of those questions so stupid that those who know what they\’re talking about will laugh.

However. CH4. Methane.

I know that it\’s possible to strip the C out using a catalyst. However, I have a feeling that it comes out as CO or CO2.

Which, if you were trying to generate energy isn\’t so bad, if you get CO you can burn that to get CO2 in a nicely exothermic reaction. And you\’ve H2 to burn, run through a fuel cell, whatever.

However, if you were trying to get rid of the CO2, not create it, you\’d much rather you got C, say as soot.

So, the question is, is there any way of stripping, reformulating, the CH4 into C plus H2s? So that you\’ve solid C which can then be disposed of?

11 comments on “Anyone know anything about catalysts?

  1. I fear that if there were such a reaction as you desire, you would very rapidly create a soot-covered catalyst, after which the reaction would stop.

  2. Tim, I dunno the answer, but I would guess that stripping H from C is endothermic, you would have to put energy into it. Of course you get the H as fuel (given that we are not using the C as fuel). So, you put energy in to strip the H, then throw away most of the energy available in the fuel by not using the carbon.

    Are you looking for a source of energy or a store of energy? Might not be any good as a source of energy.

  3. And what would you do with the soot? It is essentially carbon and it seems silly to go out of your way to turn natural gas into solid carbon while at the same time burning coal to make leccy.

    Why not just go with the exothermic reaction in the first place?

  4. You’re probably thinking about catalytic steam reforming
    CH4 + H2O -> CO + 3H2
    You do this en route to methanol or ammonia.

    To do much with just CH4 the thermodynamics says you have to get to high temperatures. People have had success with
    2CH4 -> C2H2 + 3H2
    but you have to quench the product quickly or the acetylene (ethyne) decomposes to carbon and hydrogen.
    If you google “acetylene +methane” you’ll get a couple of papers which give you the gist. For all I know ethyne +methane might give you a bit too. One process which, in its time, worked well in the lab and failed on the industrial scale was the Wulff process.

    On the whole, trying to “crack” methane is is not an attractive way to go (with the caveat that I’ve not looked at this area in years).

  5. Apologies: I got taken up with trying to remember stuff, and forgot your question. The Wulff process actually did what you want: it failed to make much acetylene but produced clouds of soot. Back in those days this was not viewed as a singular triumph. You probably don’t want to worry about a catalyst: (i) you’d probably run everything so hot that the kinetics would be the least of your worries, and (ii) as somebody remarked above, you’d just be coking your catalyst anyway.

  6. If you had lots of nuclear power stations you could use night time surpluses to produce carbon and hydrogen from methane. The carbon can be used in industrial processes or perhaps as a soil conditioner. The H2 used for energy – the H2 effectively being a (admittedly poor) way to temporarily store the nuclear electricity.

  7. “Gareth // Dec 29, 2011 at 3:33 pm

    If you had lots of nuclear power stations you could use night time surpluses to produce carbon and hydrogen from methane.”
    Surely water would be an easier source of hydrogen?

  8. You extract heat and/or work from chemical reactions when you start with elements/compounds with “high energy” (technically gibbs free energy) and end up with compounds with a “low energy”. The energy lost by the chemical system is pretty much that which you extract as heat/work. The problem with your idea of starting with methane and ending with carbon and hydrogen is that elemental carbon is not a “low energy” substance, more like “medium energy”, you can still burn graphite, as they discovered at Windscale. Carbon dioxide is a “low energy” substance and this difference in energy between elemental carbon and carbon dioxide explains why you can still burn graphite to release heat. If you stop at carbon as in your idea, you are stopping at a stage where you haven’t extracted all of the energy available in the chemical system. You may be able to do it, you just wouldn’t get much benefit from it.

  9. Same thing but put in another way. When you burn methane you get heat from the hydrogen bit of methane ending up as water and from the carbon bit ending up as carbon dioxide. If you don’t burn the carbon bit and leave it as carbon, you are not extracting the full benefit. Think buying an apple pie and not eating the pastry, it’s an expensive way to buy apples. Forgive the rambling, it’s past my bedtime!

  10. Why on earth would you want to do so?
    The best thing to do with methane is to turn it into something useful like methanol, hence dearieme’s instinctive sensible reaction.
    If you are seeking to minimise CO2, then it’s preferable to burn the methane instead of higher-order hydrocarbons, using the latter for making petrochemicals instead

  11. The main industrial production of hydrogen is by steam reformation from natural gas as dearieme said.
    It’s one of the funny things that proponents of hydrogen cars omit, it’s made using fossil fuel anyway.

Leave a Reply

Name and email are required. Your email address will not be published.

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>