Sciencemadness Discussion Board

Electrolysis of fatty acid anions?

Benj-NH2 - 21-5-2023 at 09:44

Has anyone conducted electrolysis of natural fatty acid anion (soap) solutions and analyzed the products?

I mean, it's similar to a Kolbe electrolysis, but with much more complex and diverse anions. I would like to start with natural leftover cooking oil and perform saponification with it, essentially turning it into renewable fuel using leftover materials (ignoring further needed purification...). What products would be produced? They would of course depend on the starting material and the amount of saturated/unsaturated long chain/short chain fatty acids, but theoretically, it should result in an organic layer with various hydrocarbons or possibly something more waxy...? Am I completely mistaken here? Or are there non-Kolbe products produced?

Next, what kind of electrode would be most suitable for this reaction? Graphite, platinum, or something else? And what would be the optimal reaction conditions overall? Alkaline conditions are probably required to deprotonate the fatty acids, but what about temperature?
Understanding how this reaction works would be helpful. For instance, if the fatty acid anions are reduced at the anode to produce organic products, while the Na+ ions from the soap are oxidized, you would theoretically just have to add more starting material because the needed lye for the saponification is constantly being reproduced…
you would just have to get rid of the Glycerin...

If anyone has knowledge or experience regarding this topic, please share your findings with me.

khlor - 28-5-2023 at 17:53

I remeember reading some patent on the subject, they were using around 20v and gold anodes, for the cathodes, you could use even stainles steel. the goal was to produce biofuels(with quality comparable to that of petrolleum) through this route, they were using a divided cell if I my memory is any good. the goals were somewhat met. the patent was described to work, but still is regarded as being inneficient due to the high electrical power demands.

as for doing it, I did it myself with sodium acetate(yielded ethane), I do have access to fairly clean fatty acids sodium salts, and considered to try, though assembling the reactor for that have put me off it for a few months now. if I get to do it before you, I'll remember to share my results. right now work is consuming all of my life so experiments took the back stage, but I'm making an effort to get back on the game.

here is the link for the paper in question
https://patents.google.com/patent/WO2016041065A1/en

khlor - 28-5-2023 at 18:09

Quote: Originally posted by Benj-NH2  
Has anyone conducted electrolysis of natural fatty acid anion (soap) solutions and analyzed the products?

I mean, it's similar to a Kolbe electrolysis, but with much more complex and diverse anions. I would like to start with natural leftover cooking oil and perform saponification with it, essentially turning it into renewable fuel using leftover materials (ignoring further needed purification...). What products would be produced? They would of course depend on the starting material and the amount of saturated/unsaturated long chain/short chain fatty acids, but theoretically, it should result in an organic layer with various hydrocarbons or possibly something more waxy...? Am I completely mistaken here? Or are there non-Kolbe products produced?

Next, what kind of electrode would be most suitable for this reaction? Graphite, platinum, or something else? And what would be the optimal reaction conditions overall? Alkaline conditions are probably required to deprotonate the fatty acids, but what about temperature?
Understanding how this reaction works would be helpful. For instance, if the fatty acid anions are reduced at the anode to produce organic products, while the Na+ ions from the soap are oxidized, you would theoretically just have to add more starting material because the needed lye for the saponification is constantly being reproduced…
you would just have to get rid of the Glycerin...

If anyone has knowledge or experience regarding this topic, please share your findings with me.


Yes, it is kolbe electrolysis, and yes,organinc products are formed(very long chaincarbon compounds, usually above 20 depending on the source fatty acids)

no free fatty acids needed,you can just use sodium salts(i.e. soap)

standard temperatures can be used

it would form CO2 and some long organic chain compound on the anode, if the cell is divided(recomended) sodim hydroxide on the cathode, otherwise, I assume the reaction would still occur, but instead of sodium hydroxide you would have some sodium carbonate, bicarbonate and most likely an emulsion of your product, and the starting material

you don't. if you start with free fatty acids or already made sodium fatty acids salts, glycerin is not an issue, but if you start from triglycerides, then just get rid of the glycerin through the aqueous layer(on the anode chamber of a divided cell) -------------

the operation would be simple, you don't feed fatty acids, but instead you feed fatty acids already reacted with sodium hydroxide(the fatty acids salts) then during operation the sodium ions migrate to the cathode chamber and on the anode an oily layer will start forming, that is at least how I'd start going about doing it. but people use the kolbe cell, so if it has continuous operation I don't know... take a look at what a kolbe cell looks like. it is interesting.