than NaOH+MeOH. I will try to write a chemical explanation for this in my
thesis. From an first look is seems that the K-O bond is more polar and
dissociates esterified glycerides more easily...
Some other authors have made the same conclusion (for those interesting i
can send them the whole article):
Kinetic Parameters Affecting the Alkali-Catalyzed Transesterification
Process of Used Olive Oil
M. Pilar Dorado,*,? Evaristo Ballesteros,? Martin Mittelbach,€ and Francisco
J. Lo«pez|
Departments of Mechanics and Mining and of Physical and Analytical
Chemistry,
EUP de Linares, University of Jae«n, C/. Alfonso X el Sabio 28, 23700
Linares, Jae«n, Spain,
Institute of Chemistry, Karl-Franzens-UniversitaŹ t Graz, Heinrichstrasse
28, A-8010 Graz,
Austria, and Department of Agricultural Engineering, ETSIAM, University of
Co«rdoba,
Avenida Mene«ndez Pidal s/n, 14080 Co«rdoba, Spain
Received November 21, 2003. Revised Manuscript Received June 9, 2004
In this study, chemical parameters involved in waste olive oil
transesterification were investigated and optimized. Better results were
obtained using KOH and methanol instead of
NaOH and ethanol, which decreases transesterification rates. The presence of
KOH and methanol above or below the optimum quantity decreases the ester
yield because of the presence of soaps
or unreacted glycerides, respectively. Settling at ambient temperature under
25 ĄC increases the difficulty of ester and glycerol separation because of a
conflict between glycerol solubility
and low temperatures. This could be solved by increasing the settling
temperature or the time for settling. In summary, the reaction was optimized
at ambient temperature using 1.26% KOH,
12% methanol, 1 min of stirring, with 90 min of pour-off time, 11.38%
distilled water by volume at 25 ĄC to purify the ester, and drying over 0.5%
Na2SO4. Losses of esters during the washing
process were less than 4%. The ester yield of the reaction was 94%. The
small presence of unreacted glycerides did not drop the engine performance.
Fuel specifications were close to those
of diesel fuel, thus indicating that methyl esters from used olive oil can
be considered as a fuel candidate.
----- Original Message -----
From: "Andrew Cunningham" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Thursday, January 13, 2005 10:29 PM
Subject: Re: [Biofuel] Kaliumhydroxide.
How does KOH avoid saponifcation? As far as I knew both NaOH and KOH
are equally capable of the saponification reaction.
Andy
Chemical Engineer
"If you want the opinion of a chemist, i think that KOH wich i use gives
better product yields (you avoid saponification and problems in the
cleaning)
This means that in a production cycle it may be less expensive.
Stelios"
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