I would like to get a copy of those article. Can you explain what you mean by the K-O bond being more polar? I didn't think that there were any K-O bonds left once the KOH is dissolved (reacted) with the methanol creating methoxide since that acid-bace reaction is quite complete.
Andy On Fri, 14 Jan 2005 09:27:13 +0200, Stelios Terzakis <[EMAIL PROTECTED]> wrote: > My experience about KOH+MeOH is that the path of saponification is weaker > 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" > > _______________________________________________ > > Biofuel mailing list > > [EMAIL PROTECTED] > > http://wwia.org/mailman/listinfo.cgi/biofuel > > > > Biofuel at Journey to Forever: > > http://journeytoforever.org/biofuel.html > > > > Biofuel archives at Infoarchive.net (searchable): > > http://infoarchive.net/sgroup/biofuel/ > > _______________________________________________ > Biofuel mailing list > [EMAIL PROTECTED] > http://wwia.org/mailman/listinfo.cgi/biofuel > > Biofuel at Journey to Forever: > http://journeytoforever.org/biofuel.html > > Biofuel archives at Infoarchive.net (searchable): > http://infoarchive.net/sgroup/biofuel/ > _______________________________________________ Biofuel mailing list [EMAIL PROTECTED] http://wwia.org/mailman/listinfo.cgi/biofuel Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Biofuel archives at Infoarchive.net (searchable): http://infoarchive.net/sgroup/biofuel/
