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Biodiesel & SVO Forums Home Biodiesel & SVO Forums Acid Esterification Van Gerpen's FFA stripping by ethanol?Page 1 2
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Which paper? Link please!
~Erik
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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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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? 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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Try this link ways of processing bio |
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Nope - darn. This isn't a paper and contains no useful information on the subject in question. The only mention of ethanol and FFA separation is a segment from a list. There are no references either. Thanks for posting though. ~Erik
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I e-mailed Jon a link to this discussion. Maybe something will come of it.
Kumar Plocher Yokayo Biofuels Fueled for Thought blog .........../ \.............. fueling / R \ evolution since 2001 '''''''''''''/____\''''''''''''''''''' Sustainable Biodiesel...  |
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I will have to find where I saved a paper of IPA's ability to dissolve triglycerides as well as FFA. I think it said that isopropyl will even become misible with vegoil at around 60-70C.
This isn't the article I was looking for, but it starts the discussion. This one is just talking about IPA from 75%to 99% pure so one could distill it to just the azeotrope for reuse. It could also pick up left over water from feedstock drying. The feedstock could also be re-dried after IPA/water extraction of the FFA. http://www.springerlink.com/content/4278g65134600772/ Andy |
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Still looking for the paper, gave up finding where on the hard drive it was and starting typing in statements from the paper hoping to find it via google.
Here is where it can be downloaded from: Click here http://cigr-ejournal.tamu.edu/submissions/volume8/FP%20...al%2023March2006.pdf In the process, I found a great book exactly on oil/FFA extraction: Technology and Solvents for Extracting Oilseeds and Nonpetroleum Oils http://books.google.com/books?id=jqUjKBplqPcC Pages 28-31 go over some data on oil extraction. FFA are more polar than oil so they should dissolve easier. Andy |
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| <Nick Lockard>
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Sorry gents, www.nrel.gov/docs/fy04osti/36244.pdf
I'll re-read and find the page number. To clarify since some of you have misunderstood: this is a discussion of a way to remove FFA's from WVO without reacting them by solvent stripping the FFA's from WVO prior to reaction. Edit: read page 59, second from last paragraph of the link for Trent's comments on solvent stripping of FFA's using polar solvents that are partially immiscible with triglycerides. Actually, Trent's comments are all worthy of discussion  |
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| <Nick Lockard>
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Yes, but they are so chemically similar and miscible with triglycerides; they are hard to remove with anything but a high speed, continuous liquid-liquid tubular centrifuge (huge $$.)
I think possibly. You could collect the FFA fractions from every ten batches of WVO-->bioD conversion and save them up. Then, you could spend a day just acid esterifying them separately. This is what the discussion is about. |
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| <Nick Lockard>
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"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." |
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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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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. ~Erik
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| <Nick Lockard>
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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 the correct 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. There are forward and reverse reactions possible for the class of SN2 substitutions generally referred to as hydrolysis: saponification is one. 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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| <Nick Lockard>
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I was thinking that way too. I guess it would also depend on how much evaporation happened while you were waiting to collect enough. |
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| <Nick Lockard>
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"Trans-" is a Greek prefix that is root found in a great deal of terminology. Your "non-sequiter" statement is a red herring; mistakes buried in language and terminology are still mistakes. Perhaps there is some movement among chemists to eliminate this terminology. Find me a single peer-reviewed source that states transesterification is improper terminology and I'll revise my viewpoint. Again, saponification is a hydrolysis reaction. Theres a critical difference when compared to transesterification. I have 6 university-sourced books (some Biodiesel-oriented, some O-Chem), not to mention a hoard of publications that all use the term "transesterification." Agreed; the mechanisms share this characteristic. Perhaps you're over-invested in this singular information source? Nope, but when you claim expertise and make incorrect statements, there is a need to address the issue. I don't doubt you know more chemistry than I, as I'm not an expert chemist. I can walk one building over to ask the chem profs what they think any time I wish, however. ~Erik
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I agree with you Ebztz. I once knew a young high school student whoose science teacher claimed it was impossible to boil water until it froze. He was a very good teacher but he was very wrong on that particular topic. For anyone to believe everything from one source over all else is only good in one particular instance. Thankyou Ebztz for catching the details. |
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This is exactly why we have peer-review; multiple sources (experts in the field) confirming the findings of the individual or group being published. Truly off-topic, I can say I've learned more from my students (collectively) than from my professors. Perhaps is just the sheer volume, but most of the good questions and challenges I've been issued have come from students. ~Erik
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