Hello,
I am performing esterification reactions between fatty acids and alcohols, in presence of methanesulfonic acid and H3PO2 as catalysts. At the end of the reaction, to reach the acid index I want, as well to neutralize the catalysts, I use NaOH, 30 % solution. At the end of the reaction, I perform filtration by using some powders. What I observed is that after a while the acid index increases, this being un inconvenient, because it should be in a certain range. I believe that this might be the effect of an reversible reaction, which means that the catalysts are still active.
What can I use at the end of the synthesis for the neutralization of the catalysts to be sure that the reversible reaction won't take place? or may be there are some composite able to adsorb them?
thank you in advance,
Elena
What you should do is to follow the standard workup procedure for organic reactions. Once your esterification is complete, the reaction mixture is dissolved in an appropriate water-insoluble organic solvent (ether, ethyl acetate, dichloromethane, and alike). The organic phase is then placed in a separation funnel and is washed with conc. aq. sodium bicarbonate or, to improve phase separation, a mixture of than with saturated brine. Several washings may be required to reach slightly basic pH in aqueous phase. Once this takes place, the organic phase is washed with brine, dried over Na2SO4 or MgSO4, filtered, and evaporated. Alternatively, you can neutralize the reaction mixture by gradual addition of triethylamine to a slightly basic reaction on wet pH-paper, and then proceed to the aqueous workup as above. This is recommended in cases where the ester is prone to hydrolysis under aqueous acidic conditions.
Any textbook in preparative organic chemistry describes this work-up procedure and the glassware required in detail. Another suggestion I can make is to use only methanesulfonic acid (MSA) as a catalyst. In comparison with phosphoric acid, MSA is more readily removed by washing with bases because it does not form buffered aqueous solutions to the extent phosphoric acid does. Good luck with your synthesis
Andrei Guzaev thank you for your time and support in writing this response.
Elena Grosu
It’s better to click on recommendations than to write thank you letters. They are not considered a robot.
We have industrial expertise in MSA catalyses Transesterfication. (See EP 2 464 715 - 12.08.02010 Inventor A. Ingendoh inachem GmbH). There is no need to neutralize before separation of glycerol. MSA iss very polar and is found >99% in the polar glycerol phase. This is easy, as with MSA you do not have any emulsification phase of biodiesel and glycerol phase. Separation is almost immediate and with a clear phase separation.
Once you neutralize the glycerol phase you can use what ever is best.
Regard Axel Ingendoh
Solution of NaOH in water may quickly hydrolyze the ester product. For ester-safely neutralizing acid catalysts, you may try a cooled tetrabutylammonium bicarbonate solution. Further treatment is as usual: the ester goes to the non-polar organic phase (e.g., a 4:1 hexane - dichloromethane mixture), and the salt remains in the water phase.
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