Sunlight to fuel: Cambridge’s new breakthrough in clean energy

Why not use plants instead?

Quote "Carbon Capture and Storage (CCS) has been touted as a possible solution to the climate crisis, and has recently received £22bn in funding from the UK government." /Quote

Stop this £22bn funding nonsense and the government can reverse all those measures in the last budget that are predicted to add significantly to the cost of our food, and other, bills.

Or is this just some more journalistic bullshit?

Plants take a lot of effort and inputs (land, fertiliser, water) to grow. Then you need to process them into something useful.

Being able to skip those steps has a lot of advantages. At the end of the day it's all about efficiency numbers - remains to be seen how far this could go in efficiency terms, and whether there are cases where it would make sense where you don't have those inputs.

The paper is here:

Maybe it's easier to capture the product. But following the link to their report in Nature, it looks like they are using some exotic substrates for the reaction (seems syngas is some mixture of hydrogen and carbon monoxide) but it might be a way to use waste plastic.

Yeah, that's what I looked at. It's too turgid for me to read in detail, however, and just now I'm busy doing nothing so I'll have to put off reading it carefully for a century or so.

When I came across syngas, it was to be the product of burning municipal waste in a plasma arc. The syngas first went to a heat exchanger to boil water and drive a steam turbine, then through a second heat exchanger to drive a lower pressure steam turbine, before being burnt for two gas turbines and those waste gases passed through another heat exchanger to pre-heat water for the other systems. All the turbines were to generate electricity, some of which was to be used to power conveyors, a shredder, pumps, the arc and the control system, with the rest exported to the grid. I left before build started, so I don't know how it went.

I seem to be misunderstanding something in that article. Syngas is a mixture of carbon monoxide and hydrogen. Where does the hydrogen come from? Fig.1a shows just air entering the reaction chamber. There is no mention of hydrogen at all (no green dots).

Fig1.b shows Air/N2 entering the reaction chamber. The "CO2U Unit" (light red) is shown as containing hydrogen as it has green dots. Where does that hydrogen come from? In Fig1.a the "CO2U Unit" is not shown as containing any hydrogen.

Fig.1d has a reaction at the top: CO2 + 2H+ --> CO + H2 (H2O) What does the 2H+ signify on the LHS of the equation? What does the H2O in brackets mean?

Any clarification gratefully received.

Well I dunno for sure. But the reaction seems to be taking place over a substrate of glycolaldehyde (HOCH2−CHO) and other substances. Perhaps with an input on sunlght (UV?) it catalyses the breakdown of the glycolaldehyde:

HOCH2−CHO -> 2CO + 2H2

but I'm just guessing. Do we have a real chemical engineer on the strength?

OK - belay that. The actual substrate seems to be mineral only, no organics. The glycolaldehyde and the formate appear to be outputs, not inputs.

You can process syngas. But that little reactor isn't doing that part.

If you Google your ass off, you can see all sorts of constituent parts laying about.

"Photo-driven Fischer–Tropsch synthesis"

When someone wins the Nobel Prize, they acknowledge they didn't do all the work themselves, and many people contributed papers with small hints in them, that made the discovery possible. So it will be with projects like the one above. Someone has to figure out which (set) of steps to combine, which steps require zero maintenance, which output products are unconditionally stable (and easy to collect). A project might fail, if we have to drive a truck around too long a distance, emptying the output jugs. Pipelines are extremely expensive. The last one in Canada cost $30 billion. That's enough for three reactors :-) Or about half the cost of waterproofing Manhattan against rising water levels.

Paul

Indeed. Even if the glycolaldehyde was an input, where does it come from? Its synthesis, according to the wiki, is from glycol and H2O2. And that just pushes the "hydrogen" question further down the line! There is the possibility of biosynthesis, and that's mentioned in the wiki.

Paul's reply downthread has an interesting ref at

I does seem to mention the use of waste PET as one input. That will have hydrogen in it?

nib

I can suggest this much.

It's a Redox reaction.

There are two equations, one is a reduction, one is an oxidation.

The PET and Ethylene Glycol is an attempt to clean up an industrial pollutant, via using it as part of a half reaction. The "value added chemical" notion, is the outputs are somehow easier to deal with. The glycol aldehyde dimer is supposed to be a simple sugar.

In normal chemistry notation, one of the reactions contributes something to the other reaction.

But attempts to get anything to balance, to have a net H2 output for the Syngas, haven't worked out for me. Normally, you would need some H2 to make a Syngas, but there is no source of gaseous H2 in the chamber.

The next stage after the making of Syngas, might be something like this. This could make longer chain hydrocarbons which are easier to store on site. Perhaps in a liquid form. The industrial version of this, needs energy input. Looking for a photochemsitry version, is to harvest the energy from the Sun.

"Photo-driven Fischer–Tropsch"

Paul

I can see the "green-ness" of their electron donor half reaction source material (basically it is the recycling of PET plastic). They apparently used other electron donors of lower complexity as well. Having decided to make a virtue of that feature of their scheme, they should have written up the two half reactions in standard form, for the layman to enjoy.

If the H is coming from water, show it.

If the H is coming from the PET, show it.

The important part of this paper, is the cat. Not the part about grinding up used cola bottles to make PET for recycling.

The PET + ethylene glycol they use as inputs, these are also materials found in the reaction vessel of the plant that made the PET in the first place. These are materials included as part of a reversible reaction to "unmake" the PET again. That is why those particular materials are selected. EG is an input into making PET, and having some leftovers of it when making PET, would be part of the output mixture. And then this gadget is reversing the reaction.

Paul

It's Ecobollox. It's done by Magic.

I'm replying to this, your other comments, and Nib's comment. I think your bottom line above says it all! Is this the sort of quality we can expect from one of the most prestigious scientific journals these days?

I'd noticed the pet mentioned, but it seemed to be a minor part of things as the article appeared to be about CO2 capture more than anything else. Oddly, they refer in the abstract to depolymerised pet's use in a "counter-reaction", but they haven't previously referred to the specific "reaction" which it is countering! BICBW and just missed it. One interesting thing is the method of turning waste PET into a suitable reducing agent (at the end of the section "Moist-bed gas-phase CO2 photoreduction procedure in flow"). They shred it, mix it with methanol and THF, add KOH, and stir for 24 hours at 60°C. Or it's dissolved in ethylene glycol (a by-product of the previous reaction) and reacted with KOH at 150°C for 4 hours.

According to that section the efficiency is 60%, and the methanol and THF are recovered by vacuum distillation, as is the ethylene glycol. But that's still a lot of energy required. And I wonder what the efficiency would be on an industrial scale. It's amazing how things don't scale up or down the way they do in the lab!

H+ is a hydrogen ion, an atom that's lost an electron.

That chemical equation doesn't seem balanced

CO2 + 2H+ ==> CO + H2 (H2O)

1C 2O 2H+ ==> 1C 2O 4H

Two hydrogens and two electrons have come from "somewhere", possibly UV from the sunlight is knocking electrons off the titanium dioxide, but it's still unbalanced.

This, of course, is the $64 trillion question.

Is this the new “cold fusion”, its main function being to separate gullible investors from their money?

Tim