[thaumasiotes]

> natural gas is roughly 75% hydrogen on a molar basis

I thought it was methane. Wouldn't that be 80% hydrogen on a molar basis? (Or... 67%, if we're counting moles of molecular hydrogen?) Is the discrepancy coming from impurities, or different types of fuel, or what?

[D_Alex]

Natural gas is a mixture of methane and heavier hydrocarbons, the composition varies by region, depending largely on how the LPGs (propane and butane) are used. Ethane usually ends up in natural gas, unless there is a petrochemical complex nearby.

So, 80% is a theoretical maximum, which is never achieved in practice. 75% hydrogen looks pretty right.

[thaumasiotes]

I'm still curious about the measurement "on a molar basis". If you have 20 moles of methane, and you process that to separate out the carbon, you'll end up with 20 moles of some form of carbon and 40 moles of hydrogen gas, right?

[philipkglass]

I think that "on a molar basis" is there to clarify that it's counting by number of atoms rather than grams. On a gram-for-gram basis, methane is ~75% carbon.

[D_Alex]

"Molar" refers to a number of elementary entities, which could be atoms or molecules or w/e. So yes, if you are counting moles of H2 gas, but not if you are counting atoms...

[thaumasiotes]

But hydrogen gas is the only thing you can get from that reaction. There is a theoretical construct of monatomic hydrogen, also a gas, but you're guaranteed to get molecular hydrogen instead. And there will only be 40 moles of it. There isn't a way for you to end up with 80 moles of hydrogen product.

[iamthemonster]

I'm the original commenter, and quite simply you're right and I slipped up. It's not really using the terminology correctly for me to say "natural gas is ~75% hydrogen on a molar basis".

Whenever talking about hydrogen's physical properties etc on a molar basis, we'd be talking about H2. So if you had a mole of methane (CH4) we'd say you could make two moles of hydrogen (H2) out of it.

My point was really just that the gas companies' reserves of natural gas mean that they'll do anything to try to stimulate demand for blue/grey hydrogen, because their reserves of natural gas are reserves of hydrogen.

[D_Alex]

Ooh, I love pedantry contests!

Let's go back to your opening comment which was something like "I thought methane was 80% hydrogen on a molar basis". Methane does not contain H2 molecules, it contains 4 atoms of hydrogen. Plus one atom of carbon, which would indeed make it 80% hydrogen on a molar basis.

If that does not convince you: note also that atomic carbon is also a very unstable, and will auto polymerize into one of its allotropes (eg. C60 - buckyballs). And yet we count carbon by the atom.