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What is the purpose of acid esterification?
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anaylticalchemist,

Thank you for answering and Happy New Year.

1. I use more acid because for some reason it does push the reaction further..I don't understand why, but it does..

why use more caustic?...who's using virgin WVO.. if I had virgin WVO, I most likely wouldn't using an acid stage at all. also its has been determined but many others on this forum that ASTM is not met by using 3.5 or 4.91. ASTM is what I'm trying to meet.

I agree with #1 but disagree totally with #2.
in theory you're right on #2 but in practice it doesn't work out that way. with WVO there are so many variables involved...
a short list
1. water content
2. cleaner used to clean the deep fryers
3. food...bits and pieces of all kinds
4. the oil itself. peanut, canola, soybean...
5. chemicals add to the oil..

for example, if I use 2ml of acid per liter of oil the ending titration should be 6( refer my simple above experiment), but in practice its lower than 6 without draining. so something is consuming the acid, therefore its not acting as a pure catalyst, But also as a reactant.

now if we could figure out what 'IT' is and filter/remove it from the oil before we start. that would be great, depending on what it takes to remove 'IT'.

kinda like removing water while its process...might work great in large plant, but for a home brewer it too complicated.

-dkenny


'84 bluebird school bus, DD8.2L turbo( 4/2011, the bus tranny has died..Frown 8.23.11 bus driven to scrap yard Frown )
2006 Jeep Liberty CRD Smile - the wife's
99 dodge 2500 5.9l 24v..-mine Smile
everything run B100 when its warm enough Smile
 
Location: RTP, North Carolina | Registered: December 15, 2004Reply With QuoteReport This Post
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Exactaly...if using Virgin oil...no need for the acid catalyzed method.

But by utilizing the acid to reduce/eliminate FFA, you essentially make the oil "Pseudo" virgin since it has no or very little FFA remaining. At that point, there is no need to titrate...treat it like VO.

If you're acid catalyzed step is not eliminating the FFA, then yes, I can see that a titration will be needed.

Which ASTM tests does the fuel not pass by using 3.5g NaOH or 4.91g KOH? Just curious...

-Richard
 
Location: Fayetteville, AR | Registered: February 24, 2007Reply With QuoteReport This Post
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analyticalchemist,

since titration is so easy to do. especially if the process is a batch type process, which most if not all home brewers use. I could see in an industrial process the 'rules' might change..

for the ASTM, from my understanding the total free glycerin spec is hard to meet by using 3.5g NaOH or equalivant KOH ( purity adjusted ). try running the 27/3 test on a batch.

this might also have to do with difference with just scraping in and blowing the spec away.
I recently had a sample tested at 0.1 free gly. this is way better than spec.

another thought that I had was if you're trying to reduce cost. figure out the best method to use less than 15% methanol. at the moment methanol is 4.45/gallon around my area..ouch.
this is by far the biggest cost in making biodiesel.

but for me the biggest 2 questions remain.
1. why does my method work? I use more acid than should be required, but I have 40+ batches of acid( titration from 7-27) they all worked.

2. why does the ending titration some times end below 3. more like 1.5. know why it sometimes ends above 3 but rarely above 7. drain causes a sudden drop to 3 or 4.

the 2nd question is the most puzzling. because it seems to be random.

-dkenny


'84 bluebird school bus, DD8.2L turbo( 4/2011, the bus tranny has died..Frown 8.23.11 bus driven to scrap yard Frown )
2006 Jeep Liberty CRD Smile - the wife's
99 dodge 2500 5.9l 24v..-mine Smile
everything run B100 when its warm enough Smile
 
Location: RTP, North Carolina | Registered: December 15, 2004Reply With QuoteReport This Post
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Greetings,

The acid acts as a catalyst for this reaction. The more catalyst one uses, the faster the reaction will occur. My application requires that the total process step, which includes phase separation, must be completed in an 8-hr shift. I add enough acid to achive the esterification reaction within this time constraint. The literature suggests that if one were to add the methanol to the WVO, and waited long enough, that the reaction would occur, eventually.

The variability in this reaction, IMO, is due to a number of variable properties in the initial WVO feedstock. My theory on the apparent reaction variablility is that there are 'contaminants' present that reduce ability of the acid to act like a catalyst. One of these contaminants is water. This water can either be brought into the process via the feedstock or be produced during the esterification reaction.

It should be noted that the amount of base catalyst used shouldn't really be a factor in the amount of free glycerin in the sample for ASTM spec. The free glycerin should be washed out or otherwise removed during purification following the transesterification reaction. I would say that the issue of catalyst amount has more to do with the conversion from triglyceride to ester. When the conversion is deemed not complete under the ASTM spec., this means that there is too many combined glycerides remaining in the finished ester. These combined glycerides are not water soluble and can not be washed out with water alone.

As you probably know, the more base you add, the more you increase the possibility of forming emulsions with the ester/soaps/water that can result in a loss of product as well as making the further processing of the ester messy/difficult. Again IMO, the amount of base catalyst required also can vary for the same reason as the variability of the acid catalyst.

The only way to minimize the degree of processing variability, without the expense of high level analytical work, is to know your feedstock.

Cheers,

Foxcreek
 
Location: Nova Scotia, Canada | Registered: July 17, 2005Reply With QuoteReport This Post
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this is most interesting. it appears that the technology of "acid esterizing" ,four years after i've been experimenting with it, has devolved. not to critize, but for curiosities sake:

1) could anyone send me a sample of FFA dissolved in methanol ?

2) what happened to the theory that H2SO4 was hydroscopic and by reducing the H2O content/% the biodiesel reactions (both ffa and triglycerides) went deeper -in fact(well..maybe preponderance of evidence) due to lechantlier's principle (albeit indirectly).

3)supposing you had some "top layer" other than biodiesel, determined that it was mostly methanol and also determined that the "fuel layer" was incomplete/unsatisfactory - would it be uneconomical to SPRAY 95% H2SO4 all over the top layer till most of it clouded up and sank and then mixing/heating the batch a coulpe more hours until you were pretty sure it would stay on the bottom after settled.

i'm only asking these questions to try and help clear up any possible mis-information and probably useless experiments, not because i expect an answer from obviously experienced acidbasers.

its crystal clear to me that this production method is not for the HOME brewer/chemist/scientist (although very suited to the ituitive minded). And those who would seek success at it i would suggest above all else that you put most of your effort into finding inexpensive methanol,pumps/tanks,and solvent recovery production and NOT look for a majic formula. my formula has boiled down to :

1) methanol(for the moment)/and or acid + oily goo = $$
2) if base then all manner of pastes, jellies, soapy foam + acid and more methanol = biodeisel feedstock
3) if all else fails then you can always boil/steam the suspect oil up to about 25% ffa to enable a good reaction.

**most of my failures with base method due to having inadequate triglyceride levels left from a acid first stage and contaminated titrating instruments.
 
Registered: April 26, 2005Reply With QuoteReport This Post
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China Sea Pirate,
for a sample of FFA dissolved in methanol. just take some high titrating oil, try to dissolved 20% methanol into it. the oil and methanol won't mix but the FFA and methanol do. settle and separate. you should have methanol/FFA mix and oil. the oil will also titrate lower.

2. to get the water out is the biggest challenge for the homebrewer..

3. don't know for sure but if your just trying get the "top layer" to sink and its not BD or oil. I would guess just adding water would cause the mix to sink.

I disagree that home brewers cannot get acid/base to work. I have only had 1 batch in the past 1.5 years fail. I am sure that batch had something else in the mix besides FFA that cause an initial high titration.


-dkenny


'84 bluebird school bus, DD8.2L turbo( 4/2011, the bus tranny has died..Frown 8.23.11 bus driven to scrap yard Frown )
2006 Jeep Liberty CRD Smile - the wife's
99 dodge 2500 5.9l 24v..-mine Smile
everything run B100 when its warm enough Smile
 
Location: RTP, North Carolina | Registered: December 15, 2004Reply With QuoteReport This Post



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Sory to take this old topic out. But I like learn knowledge from early stage. The topic is really interesting.


To dkenny,
For your 1st question, it is not strange that you get good result using more aicid. Althogh aicid is using as catalyst, more catalyst helps boost the reaction.

For your scond question,yes, theoretically, you should have a titration number equal or higher than 3 while you sometimes get a titration number below 3. But I don't doubt acid is just catalyst, I don't think acid is consumed during the process. I guess the reason is that the solution(oil, biodiesel, methanol, water, H2SO4) is not uniform since the methanol not dissolves in the oil. So a lot of H2SO4, water dissolve in methanol, so when you take the sample out, it is possible the titration number is not the real one. If you drained the water out, it is very possible that the titration number belows to 3 since a lot of H2SO4 was drained with the water.

The real charllenge as you mentioned is the water.

What is the most recent method to get rid of the water produced during the acid process? Using molecular sieves to make a reflux column?


quote:
Originally posted by dkenny:
analyticalchemist,

since titration is so easy to do. especially if the process is a batch type process, which most if not all home brewers use. I could see in an industrial process the 'rules' might change..

for the ASTM, from my understanding the total free glycerin spec is hard to meet by using 3.5g NaOH or equalivant KOH ( purity adjusted ). try running the 27/3 test on a batch.

this might also have to do with difference with just scraping in and blowing the spec away.
I recently had a sample tested at 0.1 free gly. this is way better than spec.

another thought that I had was if you're trying to reduce cost. figure out the best method to use less than 15% methanol. at the moment methanol is 4.45/gallon around my area..ouch.
this is by far the biggest cost in making biodiesel.

but for me the biggest 2 questions remain.
1. why does my method work? I use more acid than should be required, but I have 40+ batches of acid( titration from 7-27) they all worked.

2. why does the ending titration some times end below 3. more like 1.5. know why it sometimes ends above 3 but rarely above 7. drain causes a sudden drop to 3 or 4.

the 2nd question is the most puzzling. because it seems to be random.

-dkenny
 
Registered: February 17, 2009Reply With QuoteReport This Post
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Hey Producer and gang,

The differences in methodology and practices and theory in this particular thread are really not that far from each other. It seems often in texting and in the written post there is the tendency to amplify the differences versus reconcile them.

Please see one of the defining works by Van Gerpen regarding esterification for High FFA feedstocks, see Section 7 in:
http://www.nrel.gov/docs/fy04osti/36244.pdf
Its interesting to note: Van Gerpen states 1% catalyst by weight as a standard in industry - this is equal to ~ 9 g/liter of oil.

That section was based on his previous work with Canakci in this work: http://seniordesign.engr.uidah...hfryfuel/paper_2.pdf

When reading this work pay particular attention to Fig. 1 (water% and it's impact on the Esterification Process) and Fig. 2 (molar ratios of methanol for esterification based on FFA percentage)

Also Tables 5 and 6; talk specifically about varying catalyst amounts and its impact on forwarding the Esterfication process.

The conclusion section will answer some of the scientific questions but maybe not the real life phenomenon witnessed by many here on these pages when reacting used cooking oils.

The first thing that most people have been talking about is the water produced during the esterification reaction (condensation reaction); in a perfect reaction for every mole of Free Fatty Acid there will be the production of 1 mole of water.

The trick here is; where is the tipping point? Meaning, at what point is the water production so much that it sinks, or floats, or something in-between (yuk).

Secondly, in a perfect world a catalyst doesn't participate in the reaction by definition. However with used cooking oil and with any feedstock with FFA numbers >.05% (virgin oil number), there is soap production and then more water production and then more soap etc. (With acid, the used cooking oils tend to have other unsavory characters which don't produce soaps but do have their own side reactions none the less).

Then there is the issue of mass addition of the reactants and the mixing variables.

All this contributes to varying reaction kenetics and therefore producing different apparent results, for different people and there different processes. These things all play into the work Neutral did which demonstated that slightly more catalyst than the stoichiometric amount (3.5g NaOH or 4.9g KOH) are more ideal for encouraging the biodiesel batch reaction to ASTM levels of conversion.

This all being said (I don't have the exact numbers right now) with filtered Used Cooking Oil having <10% FFA and properly dried (<0.3% by wt.), using a limited amount of methanol (lower molar ratio) and keeping the acid to the minimum (choosing the amount best suited to this FFA percent - I favor the 1g/liter of oil) the water production is managable.

When I say managable this is because I'm not striving to get the oil to <0.5% FFA. For a successful single stage Base Catalyzed transesterification we favor <1.5% FFA (but <3.5% is very managable). This in our opinion, is a good middle ground to strive for when doing acid esterification.

Producer although some amount of FFA may be in the methanol solution - the purpose of the Acid esterification is to make higher FFA feedstocks more rapidly converted to biodiesel by using the base catalyzed reaction. Additionally and almost equally important is the increase of total yield since soap production and its emulsifying properties causes a loss of biodiesel in the settled by-product of 3 to 1 (according to Neutrals work as I'm sure you're aware of).

Also a fact that is often overlooked in this topic, is the co-solvent effect created by the resulting methyl esters produced from esterification - on the later transesterification reaction. A 10% concentration of biodiesel when added to a standard triglyceride transesterification greatly improves the reaction kenetics and can actually reduce the need to use the "generally excepted" amounts of base catalyst.

Once again making it very difficult, to say with any exactitude, as to who or what is the exactly right way!

Hope this is helpful,

GCG

This message has been edited. Last edited by: GCG,
 
Location: Michigan | Registered: May 08, 2007Reply With QuoteReport This Post
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Ok just some quick numbers to give what I said a foundation (I like my numbers round and easy)plus the numbers will be by weight, volume and moles to suit your fancy:

Let's assume our oil has been filtered and dried:
100 kg UCO (Used Cooking oil of ~100 liters)
10 kg FFA (10 wt% or ~18 by KOH titration or at ~300 g/mole a rough 33 moles)
0.1 kg Water (0.1% or 1000 ppm or 100 ml or 5.5 moles)

For a normal single stage base catalyzed transesterification we would use ~20 kg of Methanol (~25% by vol. CH3OH or 25 liters) but in this case we have to perform an Acid esterfication step first.
If we assume that the water production is managable (<1%) then we don't have to remove the methanol used during esterification and we can simply move directly to the Base reaction.

The question then is how much methanol to use for the ACID esterification step. (Gerpen talks about molar ratios of 9-40 to 1) however in their experiments they were dealing with 20% and 40% by weight FFA content where in this more typical example we have only 10%. The most typical number quoted though is a 10:1 ratio.

Most of the time in home brewing biodiesel, we think of volumes and we think of these chemical additions in proportion to the total volume of used cooking oil to be reacted. But in the second paper previously referenced Gerpen uses weight percents in relation to the total FFAs.

That means we will start our acid esterification at:
10 kg CH3OH (using ~30 g/mole this is ~330 moles of Methanol or a 10:1 molar ratio CH3OH to FFA)

Then the question is HOW MUCH acid catalyst is the most practical to use???
The first paper shows solid results with 5% by weight of the FFA's (.05 x 10,000g):
.5 kg of H2SO4 (mixed in the methanol)

Interestly enough after taking into account the differing fluid densities (1.86 g/ml H2SO4 100% and .95 g/ml oil) the amount of acid added is equivalent to ~2.5 ml per liter of all the oil.

Note that in the work done by Gerpen and Canakci they were dealing with twice the amount of FFA's typically seen by home brewers, this being the case less acid could be used than in this example especially since we have chosen to use the smallest methanol to FFA ratio which will increase the catalyst density in methanol. This is desirable since we will not be removing the methanol/water/acid/FFA mixture from the total batch volume and the acid will neutralize the base catalyst used in the final transesterification, therefore necessitating the use of more Base (more cost and more water production since when an acid and a base combine they produce a salt and water). That is why I favor the 1 ml of H2SO4 per liter of oil suggested by Analyticalchemist...


Heat to 145 deg. F and mix very vigorously (high shear preferably) for 1 - 2 hours (Gerpens work was done at 1 hour while Analyticalchemist suggest using 2 hours. By mixing longer and more vigoursly, the amount of Acid necassary can be reduced.

This process will produce about:
90 kg of Oil (~90 liters of triglyceride or 95 moles)
9.5 kg of CH3OH (~300 moles of Methanol left)
8.5 kg of Methyl Ester (biodiesel which will act as a co-solvent in the transesterification)
1.5 kg of FFA (or less, ~5 moles of FFA's)
.5 kg of H2O (34 moles of water or ~0.5%)
.5 kg of H2SO4 (some small amount used up in side reactions - unknown with UCO, ~5 moles)

To finish it off we will need to add:
10 kg of CH3OH (additional 330 moles of Methanol - > 6:1 ratio this helps with higher water content)

But how much Catalyst at this point if we are using NaOH (40 g/mole)??? Here we are on our own since both papers referenced above remove the methanol and water produced prior to base catalyzed transesterification.

Regardless, we know that we have to account for 5 moles of FFA's and the 5 moles of ACID that will immediately react producing soap, water and salt (NaSO4 is produced and it will take 2 moles of NaOH or KOH to neutralize every mole of ACID since in this example we are using H2-SO4) So at a bare minimum we have to add the stoicometric amount (3.5g x 90 liters = 315g) plus 15 moles of Catalyst (15 x 40g = 600g) this totals ~.900 kg.

We also need to take into account the water in the mix; it will hydrolize the oil and produce more soap and neutralize a portion of the catalyst but at the same time the methyl-ester produced from the FFA's will act as an intermediary (co-solvent) between the oil molecules and the methanol - I personally believe that biodiesel is a much more effective co-solvent, than water is a hydrolizer and my experience with both continuous and batch reactions confirms this, but even so the addition of a little more base is prudent.

Therefore, in this particular example I would add 1 more g/liter of triglycerides (90 grams)for:
~1 kg of NaOH (25 moles of Sodium Hydroxide).

Reheat to 145 deg. F and vigorously mix again for 1-2 hours.

GCG
(Edits include corrections for final moles of BASE necessary to perform Transesterfication reaction taking into account that every 1 mole of H2SO4 requires 2 moles of NaOH for neutralization)

This message has been edited. Last edited by: GCG,
 
Location: Michigan | Registered: May 08, 2007Reply With QuoteReport This Post
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quote:
Originally posted by GCG:
Ok just some quick numbers to give what I said a foundation (I like my numbers round and easy)plus the numbers will be by weight, volume and moles to suit your fancy:


This process will produce about:
90 kg of Oil (~90 liters of triglyceride or 95 moles)
9.5 kg of CH3OH (~300 moles of Methanol left)
8.5 kg of Methyl Ester (biodiesel which will act as a co-solvent in the transesterification)
1.5 kg of FFA (or less, ~5 moles of FFA's)
.5 kg of H2O (34 moles of water or ~0.5%)
.5 kg of H2SO4 (some small amount used up in side reactions - unknown with UCO, ~5 moles)



GCG


Thank you for working up the numbers,
I would consider the .5% H2O produced in the reaction to be on the cusp of requiring draining. That is with an estimate of .5% H2O having been present in the oil to start with (for the average hobbiest), giving us a 1% total of H2O. In my opinion above 1% H2O and yield beginns to suffer, though still much better than not using an acid stage on the same oil.
As I'm sure your aware dKenny is working to revise his formula to one that may be a bit more consistent in the other active acid thread .
I agree with you that using molar ratio's of Methanol and Acid that keep the mix suspended at your 18 KOH (which is more the upper range of most home brewers oil) is beneficial for the reason's you have mentioned.
My question then is what formula could be used that would allow for an adequete molar ratio of methanol and acid that would create an aqueous layer below the oil above T18 and keep it suspended below T18?
Or would it make for a simplified formula to keep the mix heavier than the oil at all titrations? Where it can be drained.

I see that VanGerpen was using a 10:1 Ratio in his tests but I don't see where lower molar ratios were tested. Lowering the amount of methanol used but maintaining the H2SO4 qty would effectively increase the density of the aqueous phase. It would likely increase the amount of time required above the 1hr. that Vangerpen was using. My thoughts were geared more toward allowing for evening mixing and draining the following day, as opposed to comercial production.
For oils at your T18 you could essentially add in just about all of your methanol, holding out just enough to mix your catalyst since your not going to drain. Wouldn't that esterify as much FFA as possible so then the excess base would essentially be neutralizing the H2SO4.

It takes 2moles of KOH or NAOH to neutralize 1mole H2SO4.
(2)KOH + H2SO4 -> K2SO4 + (2)H2O


Any thoughts?
 
Location: central virginia | Registered: March 13, 2008Reply With QuoteReport This Post
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DD,

Ya, that's right H2-SO4 - so in the previous post the NaOH catalyst would need to be 5 moles more or 200 grams more yielding .900 to 1.0 kg of Catalyst added to the final transesterification stage.

I'll make the corrections in the previous post to reflect this.

And Yes - the methanol amount used in the initial ACID stage should be more than the 10 kg stated but I did this only as an example and to make the numbers easier/simpler...

I also would utilize just enough methanol in the second stage BASE reaction to handle the additional NaOH added.

Please note that the initial water content is 0.1% plus the 0.5% (and yes this is about 2 times what I normally strive for in my single stage base reactions).

If you wanted to settle the reaction everytime, it is always possible to shut the reaction down at the end by adding water similar to the 5% prewash used at the end of a standard BASE reaction. However it would hardly be necessary to add this much.

Another trick would be a partial settlement after the ACID reaction. Taking out only part of the methanol and water content - just enough to ensure the water content was less than say 0.5%.

Thanks,

GCG
 
Location: Michigan | Registered: May 08, 2007Reply With QuoteReport This Post
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GCG

-when you use the acid treatment on the T18 KOH wvo. try drying it more,500ppm or less. If you do this ,you should be able to get the t down to 1 or 1.5 it one step. now of course, water is made in this process, and the main effect is that it contaminates the methanol that was used in the process, To compensate for this, on the last two batches, I considered the methanol at 30% contaminated, and added that much more to the base stage, the results where very very good. Tom


" I don't know what I don't know until I know"
1994 GMC 6.5 Tubo 2005 Dodge ram 3500, 3 VW's 2000, 2002, 2005.
 
Location: Manitoba Canada | Registered: March 24, 2009Reply With QuoteReport This Post



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Hi Double D,

So you believe the wvo with a water contain about 1% doesn't hurt in the base process? Do you have any idea of the yield with a 1% water content feedstock? Let's say if the water content is 0%, the yield should be around 100%, with water content of 1%, what's the final yield?

Thanks.


Thank you for working up the numbers,
I would consider the .5% H2O produced in the reaction to be on the cusp of requiring draining. That is with an estimate of .5% H2O having been present in the oil to start with (for the average hobbiest), giving us a 1% total of H2O. In my opinion above 1% H2O and yield beginns to suffer, though still much better than not using an acid stage on the same oil.
As I'm sure your aware dKenny is working to revise his formula to one that may be a bit more consistent in the other active acid thread .
I agree with you that using molar ratio's of Methanol and Acid that keep the mix suspended at your 18 KOH (which is more the upper range of most home brewers oil) is beneficial for the reason's you have mentioned.
My question then is what formula could be used that would allow for an adequete molar ratio of methanol and acid that would create an aqueous layer below the oil above T18 and keep it suspended below T18?
Or would it make for a simplified formula to keep the mix heavier than the oil at all titrations? Where it can be drained.

I see that VanGerpen was using a 10:1 Ratio in his tests but I don't see where lower molar ratios were tested. Lowering the amount of methanol used but maintaining the H2SO4 qty would effectively increase the density of the aqueous phase. It would likely increase the amount of time required above the 1hr. that Vangerpen was using. My thoughts were geared more toward allowing for evening mixing and draining the following day, as opposed to comercial production.
For oils at your T18 you could essentially add in just about all of your methanol, holding out just enough to mix your catalyst since your not going to drain. Wouldn't that esterify as much FFA as possible so then the excess base would essentially be neutralizing the H2SO4.

It takes 2moles of KOH or NAOH to neutralize 1mole H2SO4.
(2)KOH + H2SO4 -> K2SO4 + (2)H2O


Any thoughts?[/QUOTE]
 
Registered: February 17, 2009Reply With QuoteReport This Post
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quote:
Originally posted by Green energy:
Hi Double D,

So you believe the wvo with a water contain about 1% doesn't hurt in the base process? Do you have any idea of the yield with a 1% water content feedstock? Let's say if the water content is 0%, the yield should be around 100%, with water content of 1%, what's the final yield?

Thanks.


]


My current UCO of mixed feedstock typically registers .3% -.5% H2O before processing and I average
about 95% yield. This oil routinely titrates at 1.5-2.5ml KOH(93%). I have been using a single base stage on this oil. Just over 1% with this oil would not be a problem cracking but yield would decrease due to more soap formation. I say 1% as a general rule mainly because slightly higher titrating oil and excessive water are ingredients for poor conversion, and excessive soap formation.
There are alot of other variables that can inhibit the reaction efficiency as well. Processor design, mixing vigor, methoxide injection, temperature, duration, etc. All these things can impact final yield.

I could work up the theoretical amount by the math but all that can give you is a general idea since there are so many variables.
 
Location: central virginia | Registered: March 13, 2008Reply With QuoteReport This Post
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Thanks Double D.

][/QUOTE]

My current UCO of mixed feedstock typically registers .3% -.5% H2O before processing and I average
about 95% yield. This oil routinely titrates at 1.5-2.5ml KOH(93%). I have been using a single base stage on this oil. Just over 1% with this oil would not be a problem cracking but yield would decrease due to more soap formation. I say 1% as a general rule mainly because slightly higher titrating oil and excessive water are ingredients for poor conversion, and excessive soap formation.
There are alot of other variables that can inhibit the reaction efficiency as well. Processor design, mixing vigor, methoxide injection, temperature, duration, etc. All these things can impact final yield.

I could work up the theoretical amount by the math but all that can give you is a general idea since there are so many variables.[/QUOTE]
 
Registered: February 17, 2009Reply With QuoteReport This Post
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quote:
Originally posted by GCG:
DD,

Ya, that's right H2-SO4 - so in the previous post the NaOH catalyst would need to be 5 moles more or 200 grams more yielding .900 to 1.0 kg of Catalyst added to the final transesterification stage.

I'll make the corrections in the previous post to reflect this.

And Yes - the methanol amount used in the initial ACID stage should be more than the 10 kg stated but I did this only as an example and to make the numbers easier/simpler...

I also would utilize just enough methanol in the second stage BASE reaction to handle the additional NaOH added.

Please note that the initial water content is 0.1% plus the 0.5% (and yes this is about 2 times what I normally strive for in my single stage base reactions).

If you wanted to settle the reaction everytime, it is always possible to shut the reaction down at the end by adding water similar to the 5% prewash used at the end of a standard BASE reaction. However it would hardly be necessary to add this much.

Another trick would be a partial settlement after the ACID reaction. Taking out only part of the methanol and water content - just enough to ensure the water content was less than say 0.5%.

Thanks,

GCG


I'm definately in favor of draining part (not so much the adding H2O) of the lower phase if necessary, to reduce the water qty prior to the base stage.

I know many of us could do the calculations for each batch or create a long formula to fill in that we could use to control the amounts but who want's to have to do that for every batch.
Dkenny's formula of T-3 x.02 is an easy one to remember and not alot of numbers that I can mess up just as with the base stage NaOH ~5g+T it's quick and easy.

Any thoughts on a quick simple formula for AE that's effective over a wide range of titrations?
 
Location: central virginia | Registered: March 13, 2008Reply With QuoteReport This Post
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