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Originally posted by Nick Lockard:
Has anyone tried stripping FFA's with warm ethanol?

It's suggested in one of Van Gerpen's papers as a possible method for handling high FFA feedstock. After stripping, the WVO could be base esterified and the ethanol/FFA mix acid catalyzed separately.

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The FFA's have no strong attraction to any alcohol by itself to enable you to separate them from the triglycerides.

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Van Gerpen's papers as a possible method for handling high FFA feedstock

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Originally posted by sinbad:

Try this link
ways of processing bio

~Erik

Useful Biodiesel-related links Support International Microbusiness - Kiva "The ability to defend a position does not make you wise in doing so." "I'm after sustainable, independent, sensible energy use and application, regardless of what particular energy carrier that may entail. "

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Since the FFAs are FREE, wouldn't they be relatively easy to seperate? I mean, aren't they essentially just chains of fatty acids broken off the original triglyceride molecules? (like branches broken off a tree)

Aren't they free to move in the veggie oil almost like dissolved fuel additives, rather than chemically bonded components? If FFAs are truly free, I can't help but wonder if an even very small difference in weight between FFAs and mono/di/triclycerides couldn't be used as a means of centrifugal seperation via a continuous process extremely high G-force centrifuge?

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Then again, since seperated FFAs would still need conversion, would it even worth it to seperate them out of the rest of the oil rather than simply using a 2 stage esterification/transesterification process?

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Originally posted by PGBiodiesel:

quote:

Originally posted by Nick Lockard:
Has anyone tried stripping FFA's with warm ethanol?

It's suggested in one of Van Gerpen's papers as a possible method for handling high FFA feedstock. After stripping, the WVO could be base esterified and the ethanol/FFA mix acid catalyzed separately.

Yes, I also would like the link.

The triglycerides(WVO) are transesterified with a base catalyst not esterified. You can esterify FFA's with ethanol as well as methanol if you use a strong acid catalyst. The FFA's have no strong attraction to any alcohol by itself to enable you to separate them from the triglycerides.

Heat, below vaporization, will speed up most chemical reactions. Converting VO to Biodiesel is a chemical reaction, not a dilution.

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It's suggested in one of Van Gerpen's papers as a possible method for handling high FFA feedstock. After stripping, the WVO could be base esterified and the ethanol/FFA mix acid catalyzed separately.

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Originally posted by Nick Lockard:
"transesterification" is a misnomer that us chemists hate

The proper chemical name for base catalyzed esterification is the saponification reaction. Or, more precisely, "SN2 substitution reaction."

~Erik

Useful Biodiesel-related links Support International Microbusiness - Kiva "The ability to defend a position does not make you wise in doing so." "I'm after sustainable, independent, sensible energy use and application, regardless of what particular energy carrier that may entail. "

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Originally posted by ebztz:

quote:

Originally posted by Nick Lockard:
"transesterification" is a misnomer that us chemists hate

The proper chemical name for base catalyzed esterification is the saponification reaction. Or, more precisely, "SN2 substitution reaction."

I'm not sure which chemist you're referring to as "we," but this simply is false.

Saponification is a hydrolysis reaction that forms salts of carboxylic acids (soap). Methyl esters are NOT salts and saponification is an undesirable side reaction. Transesterification, or substitution of alcohols, is the appropriate reaction descriptor.

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Originally posted by RickDaTech:

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It's suggested in one of Van Gerpen's papers as a possible method for handling high FFA feedstock. After stripping, the WVO could be base esterified and the ethanol/FFA mix acid catalyzed separately.

Assuming the ethanol:FFA ratio is low, couldn't the ethanol be used once acid esterified as a portion of the alcohol used in the base reaction? Water content would obviously be the limiting factor.

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Originally posted by Nick Lockard:

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Originally posted by ebztz:

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Originally posted by Nick Lockard:
"transesterification" is a misnomer that us chemists hate

The proper chemical name for base catalyzed esterification is the saponification reaction. Or, more precisely, "SN2 substitution reaction."

I'm not sure which chemist you're referring to as "we," but this simply is false.

Saponification is a hydrolysis reaction that forms salts of carboxylic acids (soap). Methyl esters are NOT salts and saponification is an undesirable side reaction. Transesterification, or substitution of alcohols, is the appropriate reaction descriptor.

Well, we'll have to agree to disagree because my O-chem prof hated "transesterification" and so do I. In chemistry, "trans" refers to a double bond arrangement, which has absolutely nothing to do with this reaction and is a misleading non sequiter.

Saponification IS an appropriate (if somewhat sloppy) term, despite what you learned on the interweb. It just happens that instead of an -OH nucleophile, we have placed a better nucleophile (methoxide anion) there, but the reaction mechanism is the exact same SN2 substitution reaction which proceeds through a tetrahedral carbanion reaction intermediate.

Unfortunately, even the O-chem text author (Jones, 2nd Ed. Organic Chemistry) uses sloppy language here, and chemists are often lazy in using the same reaction names for both the forward and reverse reactions

So, let's just call it SN2 substitution, eh

When Wikipedia and my former O-chem prof disagree...O-chem prof wins.

Are we on topic???

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Originally posted by Nick Lockard:
Well, we'll have to agree to disagree because my O-chem prof hated "transesterification" and so do I. In chemistry, "trans" refers to a double bond arrangement, which has absolutely nothing to do with this reaction and is a misleading non sequiter.

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Saponification IS an appropriate (if somewhat sloppy) term, despite what you learned on the interweb. It just happens that instead of an -OH nucleophile, we have placed a better nucleophile (methoxide anion) there, but the reaction mechanism is the exact same SN2 substitution reaction which proceeds through a tetrahedral carbanion reaction intermediate.

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Unfortunately, even the O-chem text author (Jones, 2nd Ed. Organic Chemistry) uses sloppy language here, and chemists are often lazy in using the same reaction names for both the forward and reverse reactions

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So, let's just call it SN2 substitution, eh

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When Wikipedia and my former O-chem prof disagree...O-chem prof wins.

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Are we on topic???

~Erik

Useful Biodiesel-related links Support International Microbusiness - Kiva "The ability to defend a position does not make you wise in doing so." "I'm after sustainable, independent, sensible energy use and application, regardless of what particular energy carrier that may entail. "

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Originally posted by ebztz:
Find me a single peer-reviewed source that states transesterification is improper terminology and I'll revise my viewpoint.

Perhaps you're over-invested in this singular information source?

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Are we on topic???

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Nope, but when you claim expertise and make incorrect statements, there is a need to address the issue.

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Originally posted by PGBiodiesel:

For anyone to believe everything from one source over all else is only good in one particular instance.

~Erik

Useful Biodiesel-related links Support International Microbusiness - Kiva "The ability to defend a position does not make you wise in doing so." "I'm after sustainable, independent, sensible energy use and application, regardless of what particular energy carrier that may entail. "