Author Topic: Ethanol FROM CO2 - New cataylst process  (Read 5592 times)

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Offline Cerebus

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Re: Ethanol FROM CO2 - New cataylst process
« Reply #25 on: October 20, 2016, 04:06:30 pm »
The trick is that you need a CO2 supply. So there are not very many places that would be suitable.

Breweries, bakeries, the list could be quite long; but if I had somewhere that produced beer, bread and fuel for my car I'd have a goodly proportion of the things that I think are essential in life.  :)
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Offline Cerebus

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Re: Ethanol FROM CO2 - New cataylst process
« Reply #26 on: October 20, 2016, 04:16:22 pm »
In chemistry yield usually refers to the percentage of a chosen starting material that was converted to the target compound. So 63% yield means that 63% of starting CO2 was converted to ethanol. Energy use is not accounted for in chemistry papers.
The yield is a way to quantify how selective the reaction is, since more side-products lower the yield. Some of the product is lost during purification, which also lowers it.

Here's the abstract of the actual paper that the article is about:

Quote
Though carbon dioxide is a waste product of combustion, it can also be a potential feedstock for the production of fine and commodity organic chemicals provided that an efficient means to convert it to useful organic synthons can be developed. Herein we report a common element, nanostructured catalyst for the direct electrochemical conversion of CO2 to ethanol with high Faradaic efficiency (63?% at ?1.2?V vs RHE) and high selectivity (84?%) that operates in water and at ambient temperature and pressure. Lacking noble metals or other rare or expensive materials, the catalyst is comprised of Cu nanoparticles on a highly textured, N-doped carbon nanospike film. Electrochemical analysis and density functional theory (DFT) calculations suggest a preliminary mechanism in which active sites on the Cu nanoparticles and the carbon nanospikes work in tandem to control the electrochemical reduction of carbon monoxide dimer to alcohol.

So for yield substitute Faradaic efficiency.

Actual paper is  http://dx.doi.org/10.1002/slct.201601169.

Edited to add:

This is an example of something that really ticks me off - mangling of clear information in a scientific story as it gets written up by a journalist even in decent publications such as New Scientist, Scientific American, or in this case Science Daily. Don't get me started on medical research as reported by the likes of the Daily Fascist Mail*.

*The Daily Mail were enthusiastic supporters of the British Fascist Movement even after it had become clear to everybody else what Fascism, Hitler and Mussolini were really all about. Their approach to politics these days is just as nuanced as it was then and I consequently take every opportunity to remind the world quite how sound the editorial opinions of this organ have been proved to be.
« Last Edit: October 20, 2016, 04:28:11 pm by Cerebus »
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Offline helius

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Re: Ethanol FROM CO2 - New cataylst process
« Reply #27 on: October 20, 2016, 05:23:54 pm »
That makes it a lot clearer, thanks for reading the paper so I don't have to!
63% Faradaic efficiency is low compared to a Li-ion cell, but not terrible for many electrochemical reactions.
The emphasis in the paper seems to be on a new area in CO2 chemistry and not as a "green energy" project.
 

Offline mikeselectricstuff

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Re: Ethanol FROM CO2 - New cataylst process
« Reply #28 on: October 20, 2016, 05:33:48 pm »
63% Faradaic efficiency is low compared to a Li-ion cell, but not terrible for many electrochemical reactions.
And unlike batteries, if you need more storage capacity, all you need is a bigger tank!
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Offline raptor1956

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Re: Ethanol FROM CO2 - New cataylst process
« Reply #29 on: October 20, 2016, 07:56:02 pm »
Did they mention its use as a scrubber for things like coal fired power plants?


Brian
 

Online NANDBlog

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Re: Ethanol FROM CO2 - New cataylst process
« Reply #30 on: October 20, 2016, 08:08:38 pm »
Did they mention its use as a scrubber for things like coal fired power plants?


Brian
I'll try to explain it in a simple way.
C+O2 = CO2 generates 1 Energy.
CO2 + H2O = alcohol requires 3 energy.
 

Offline Cerebus

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Re: Ethanol FROM CO2 - New cataylst process
« Reply #31 on: October 21, 2016, 12:46:02 am »
Did they mention its use as a scrubber for things like coal fired power plants?


Brian
I'll try to explain it in a simple way.
C+O2 = CO2 generates 1 Energy.
CO2 + H2O = alcohol requires 3 energy.

A clearer way of putting it, is to to say that scrubbing CO2 using a process like this would consume at least as much energy as was produced by the process that liberated CO2. Add inefficiencies and you end up with a net energy loss.

To put some hard numbers on it:- Every megajoule of energy obtained from burning coal* liberates 2 mols of CO2. Every megajoule of energy obtained from burning ethanol liberates 1.6 mols of CO2 - a perfect process for making ethanol from CO2 would use the same amount of energy. That is, you can only pack away 1.6 mols worth of CO2 from coal with the energy liberated in creating 2 mols of CO2. Thus you're already on the losing side of the energy equation before any process loses.

*The assumption used where I lifted the figures from is that the C:H ratio in the coal burned is 1:1 which is about right.
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Online Someone

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Re: Ethanol FROM CO2 - New cataylst process
« Reply #32 on: October 21, 2016, 02:52:41 am »
63% Faradaic efficiency is low compared to a Li-ion cell, but not terrible for many electrochemical reactions.
And unlike batteries, if you need more storage capacity, all you need is a bigger tank!
Range scaling of vehicles is discussed in "Sustainable Energy – without the hot air" and the incremental weight/size of more batteries eats into the energy efficiency of electric cars somewhere around 500-700km range, if you need to go further without taking on more energy then the fossil fuels are superior.
People always quote this energy density thing, but this is a pretty moot point as I'd venture to say above 70% of automotive road journeys probably fall into the range limitations of modern EV's.
Doesn't change a thing, even if you CAN do most of your travels with an EV people don't buy one if they can't do that occasional long trip with it which requires them to either own a 2nd vehicle or to rent one for way too many $$. Thresholds vary, but I'd say if you know it won't make it >10% of the time most wouldn't do the jump.
It really depends where you live, rent/hiring vehicles is commonplace and cost effective in Australia but it still doesn't make sense to jump to an electric car because of the relative fuel costs:
https://www.eevblog.com/forum/chat/problems-if-we-all-had-tesla-cars/msg705793/#msg705793
Otherwise I'd be building a small electric car with a range of 200km and renting something else as needed. Run the maths yourself, its not possible to make such broad statements on a world scale.
 


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