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CO2 To Ethanol In One Step With Cheap Catalyst (sciencedaily.com)
Reader networkBoy writes: Boffins at ORNL (Department of Energy's Oak Ridge National Laboratory) have discovered a simple and cheap catalyst that can take CO2 (Carbon Dioxide) dissolved in solution with water and at room temperature convert it to ethanol with 60%+ yields. They envision it as a way to store surplus power from green energy plants and then burning it to fill in lulls in supply.From the report:The team used a catalyst made of carbon, copper and nitrogen and applied voltage to trigger a complicated chemical reaction that essentially reverses the combustion process. With the help of the nanotechnology-based catalyst which contains multiple reaction sites, the solution of carbon dioxide dissolved in water turned into ethanol with a yield of 63 percent. Typically, this type of electrochemical reaction results in a mix of several different products in small amounts. "We're taking carbon dioxide, a waste product of combustion, and we're pushing that combustion reaction backwards with very high selectivity to a useful fuel," Rondinone said. "Ethanol was a surprise -- it's extremely difficult to go straight from carbon dioxide to ethanol with a single catalyst."
Which efficiency?
Energy use wise, or product synthesis wise?
The summary gives the latter at just over 60%.
The former? Who knows?
I am more interested in how sensitive to poisoning the catalyst is. Would exposure to salt water damage it, for instance.
If not, then huge installations of these in the open ocean coupled with tidal force generators or wave mechanic generators for the electrical power needed could make drilling for oil obsolete, while simultaneously directly removing the cause of ocean acidification. Win win.
Here's a link to the actual paper.
(Since the editors won't do it.)
The catalyst looks pretty good. I'd be interested to see how long it lasts - some catalysts become poisoned by impurities in the source gasses, and lose effectiveness over time.
The paper mentions copper oxide forming on the copper nanoparticles due to transport in the air to the test equipment. That probably means that the catalyst might lose effectiveness due to dissolved oxygen in the water.
Any actual chemists care to comment?
For this reaction, you need BOTH CO2 (from burning fossil fuels) AND "free energy" (noon solar on cloudless days).
The otherwise wasted energy from the unreliable renewable sources is used to convert CO2 into fuel.
The summary is misleading; a look at the paper reveals the 63% is the Faradic efficiency, at a current of -1.2 volts.
To collect the ethanol, the water being treated needs to be isolated from the rest of the reactant supply (aka, the ocean). The availability of local power from ocean wave generators, or tidal generators means the expense of using reverse osmosis is possible to account for. We don't need a membrane that makes clean water, just one that holds ethanol in, and that keeps plankton and microbes out.
Ethanol is a fairly large molecule (compared to salt, or co2), and microbes are downright huge in comparison.
Automated jets of ocean water against the membrane to knock plankton off every so often, coupled with a maintenance schedule, and such platforms could be extracting ethanol in huge amounts cheaply, expelling very clean ocean brine.
Assuming the catalyst can endure salt being present anyway.
"Why should I listen to someone that doesn't know the difference between affect and effect?"
I don't know. However, since I used "affected" correctly that statement has nothing to do with my post.
AntiFA: An abbreviation for Anti First Amendment.
His/her question is good, and the summary is incomplete. It converts CO2 to CH3CH2OH at a yield of about 63%, but what CO2 concentration in the water are they assuming? Average soda concentration is about 0.12-0.15 M (moles per liter) at about 4 bar. That would mean you'd get 0.05 M alcohol (2 carbons per EtOH from one carbon in CO2, 0.5*0.63*0.15), which is 0.05 moles EtOH/55.5 moles water or about 0.08 percent alcohol by volume. That's a lot less than the ethanol conversion you'd get from corn.
It did not mention the catalyst materials cost, nor the materials processing required to make a nanomaterial.
So we'd have energy costs by compressing CO2, then converting it using the catalyst, then there would be ethanol separation costs (with requisite electricity/natural gas from the distillation columns) from water that far exceed normal ethanol separation, and the ethanol would still have about 10% water because it is an azeotrope,so then you'd need another liquid-liquid extraction...
As is the case with the other carbon dioxide conversion schemes, it's really cool chemistry, looks good in summary, but the details render it ineffective for practical use.
"Who are you?" "No one of consequence." "I must know." "Get used to disappointment."
Hmm, it seems the laws of thermodynamics are being overlooked here...
Nah, we don't normally care if yeast die by the billions, and they're exceedingly unlikely to initiate an armed revolt to avoid starving to death.
--- Most topics have many sides worth arguing, allow me to take one opposite you.
It's a flavor of an obscure Germanic language spoken by a large portion of the civilized people in this place called 'America.' You may have heard of it. We're renowned for our trucks and our elevators, as well for as our scientists and engineers. No boffins though.
As I read it, TFA _does_ give a clue as to efficiency.
60% of the electrons are used for producing ethanol.
Equilibrium potential for the ethanol reaction is 84 mV.
The total voltage that is used is 1.2V, which is 14 times as high.
That means that only 7% of the voltage is used effectively.
This gives a total energy of a little over 4%.
In the conclusion, this is mentioned as "The overpotential (which might be lowered with the proper electrolyte, and by separating the hydrogen production to another catalyst) probably precludes economic viability for this catalyst"
So, they don't (dare to) mention efficiency directly, but data is presented by which it can be calculated.