[Vico]

Hello,

I'm new here, I've an school project and I'm stucked, I hope you can help me please.

Here's my problem. I'm (theoretically) preparing methyl esters of fatty acids with methanol and sodium hydroxide from oil. During the process there occurs soaps (R-COONa) but I don't know how to purify the mixture to only get R-COOCH3 (from lipids).

I was considering extraction of R-COONa with polar extractor, but I'm not sure if CH3- in R-COOCH3 is enough to protect those molecules from extraction to polar extractor too.

Then I was also considering if high pH (because theres a lot of NaOH) could make emulsion where R-COONa would be separated from the mixture by filtration, but still not sure if it's possible, or do could you propose another method, please?

Thank you very much.

[eugenedakin]

Hi Vico,

It sounds like you are making Biofuel.

Usually, the glycerine has a higher freeze point and a lower density. As long as there is no excess methanol, you should be able to cool the mixture of glycerine and methyl esters, and the methyl esters will remain as a liquid on the bottom, while the top will harden and form a waxy surface which can literally be picked out with your fingers (as a solid).

You want to minimize a high pH. Many of the seals and some metals don't like the high alkalinity of caustics.

Best wishes,

Eugene

[Vico]

eugenedakin:

You are right, my project is biofuel and biogas, it's almost complete but I'm not sure about R-COONa, I used same way as you described to remove Glycerin, but there are still free fatty acids from oil which react with NaOH and form soaps. But I'm not sure how to get rid of those fatty acid derivatives.

About methanol, task says to work in excess of methanol and NaOH.

Thank you very much for your advice.

[eugenedakin]

Hello Vico,

Although the task says to have excess methanol during the reaction phase, you need to distill the methanol from the neutralized fatty acids and glycerine at the end of the reaction. Otherwise the methanol will mix with the glycerine and you will not separate much glycerine from the fatty acids.

You cant get rid of the fatty acids because this is the component of the biofuel (this is what you are making - and is the biofuel). You can't get rid of the fatty acid derivatives, you can only neutralize them to a neutral pH. If you have soaps forming (a soap is glycerine plus fatty acids chemically reacted together), then there was either insufficient heat, time, or methanol + sodium hydroxide to complete the reaction.

I hope this helps,

Eugene

[PolymerKnowHow]

Have you tried a water wash?