50kW Solar Tower Produces Jet Fuel in the Field

Rocky Mudbutt writes:

As noted in Daily Kos,

[...] So I was really impressed to see that a collaboration among the ETH Zurich and a few other Eurpoean organizations actually built a plant that, in real sunlight, out in the field, converts carbon dioxide and water into aviation fuel. This is the first time anyone has ever actually done this for real. Check it out in the July 20 edition of the Cell Press journal Joule .

[...] At the center of this process is an inexpensive and durable catalyst called ceria, or cerium(IV) oxide.

If we heat ceria to a very high temperature (here they used 1,500C), we can strip off some of its oxygen atoms. Its crystal structure won't change; we'll just have vacancies where the dislodged oxygen atoms were. Those oxygen atoms will form O₂ gas up off the surface, so we can blow or vacuum that O₂ away to keep it from re-reacting with the ceria.

So now, what we're left with is an angry material that really, really wants its oxygen atoms back. If we spray it with some water vapor, it'll rip O right off of H₂O and give us H₂ (hydrogen gas). Or, if we blow some CO₂ over it, it'll likewise yank off an O and give us CO (carbon monoxide). These reactions are so vigorous that they actually produce a lot of heat, so it's best to let the stripped ceria cool down a bit before going to this step (that is, stop shining sunlight on it). When we're done, we have good old regular ceria back, and we can keep using it over and over again.

Because we can control how much H₂O and CO₂ we put in, we can make exactly the ratio of H₂ and CO that we want. The H₂-CO mixture we make is called synthesis gas, or syngas. Our H₂ and CO are much more reactive than H₂O and CO₂, so now we're in really good shape to build some bigger molecules out of them.

We do that with the Fischer-Tropsch process, which is very well-established.

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