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Ten Most Common Ways to Screw-Up Making BD.

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May 28, 2012, 11:19 PM
dckfly
Ten Most Common Ways to Screw-Up Making BD.
quote:
Hello ,
I am new at this so i could really use your help in biodiesel transesterification reaction.
I use SVO and i added methanol 6:1 ration of methanol to oil. however the KOH content was 0.5% the reaction was performed under 120 F . I couldn't get any biodisel .
Can i know a small experiment that will lead to biodisel separation with exact amount of methanol and catalyst with reaction time.


Go online and search for "how to make biodiesel". Many resources out there.

Try this one: http://www.make-biodiesel.org/

Have fun


Dana Knight "dckfly"
Boulder, CO

Chevy Silverado Duramax
3 VW TDI (wife and friends)
May 29, 2012, 01:26 AM
maroulla
hello ,
Thank you a lot. No i did not titrate the oil before usage.
Should i titrate it to get the exact amount of catalyst used?
Thank you


maroulla el khoury
May 29, 2012, 01:54 AM
Johann Cape Town
Don't try to drain 400L of finished bio into a 200L container. Even if you try three times the outcome is the same. Frown

I'm not too sure about the methanol evaporation risk iro completing a reaction. I process through to demething in one non stop operation and an insignificant amount of methanol collects in the receiver until the batch reaches 80 deg C. Certainly at 70 deg C evaporation condensation over a two hour process period is negligible. I have no experience of air mixing which may differ of course.
May 29, 2012, 12:18 PM
RickDaTech
quote:
Originally posted by maroulla:
hello ,
Thank you a lot. No i did not titrate the oil before usage.
Should i titrate it to get the exact amount of catalyst used?
Thank you


Yes.



Rick





www.Make-Biodiesel.org





May 30, 2012, 12:36 PM
dckfly
quote:
Don't try to drain 400L of finished bio into a 200L container. Even if you try three times the outcome is the same.


Happy to see I'm not the only one to experience this phenomenon. Lots of kitty litter used...


Dana Knight "dckfly"
Boulder, CO

Chevy Silverado Duramax
3 VW TDI (wife and friends)
August 21, 2013, 11:46 PM
LLee
I would like to expand # 1 on Graydon's list to - Anything that introduces water into the reaction. Whether it is wet oil, low purity methanol, or left over water in the processor - it will screw up your reaction.

Also - how about forgeting to triple check all your valves before starting a batch. Anyone else ever start filling the processor with the drain valve open? Or better yet, fill the processer with oil, turn on the pump and find the valve open that goes to the wash tank - where your freshly finished last batch of biodiesel is?
August 22, 2013, 10:46 AM
Ryan P.
quote:
Anyone else ever start filling the processor with the drain valve open?


I've started filling my settle/wash tank with the drain valve open...into the tank, and onto the floor....

Or turned on the recirculation pump and had the pressurize outlet hose valve open....so I am pumping the biodiesel out onto the wall where the hose is rolled up....and down onto the floor....
May 10, 2016, 06:23 AM
Jack Sparrow
Hi Everyone.
I have been working on producing biodiesel from crude jatropha curcas oil. i'm having no clue on what went wrong and where. The product of esterification using acid as catalyst seems pretty good. the FFA content is reduced to below 0.5. After that i carried out transesterification with methanol + NaOH (2% w/w of oil) as catalyst. after recovering the upper layer of biodiesel and discarding bottom layer glycerol, i attempted to wash it. but as soon as i pour warm water on biodiesel and mix it, soapy foam appears to form. can you pls point out what might be causing this. thank you very much in advance.
Cheers Smile
May 10, 2016, 06:54 AM
Paulus
What is the FFA content before acid esterification?
May 10, 2016, 07:23 AM
Jack Sparrow
quote:
Originally posted by Paulus:
What is the FFA content before acid esterification?


hi Paulus,
thank you for your response!!
before it was 16.4% ( in crude oil) and after esterification it got reduced to <0.5 %

regards!
May 10, 2016, 08:18 AM
Tilly
Hi Jack, welcome to the forum!

quote:
Originally posted by Jack Sparrow:
The product of esterification using acid as catalyst seems pretty good. the FFA content is reduced to below 0.5.
How are you measuring FFA%



quote:
After that i carried out transesterification with methanol + NaOH (2% w/w of oil) as catalyst.
One litre of jatropha curcas oil weighs approximately 920g. 2% of 920 is about 18.4g of NaOH per litre of WVO in the reactor.
Most people would use around 6g- 7g NaOH to react a litre of WVO titrating around 1.
It would appear you are using too much NaOH in your reaction and producing excessive soap.

It would be more meaningful to most people on this forum if, when you post quantities, you would post the amount of methanol used in milliliters (ml) and the amount of NaOH in grams (g) per litre of WVO in the reaction.






May 11, 2016, 06:48 AM
Jack Sparrow
quote:
Originally posted by Tilly:
Hi Jack, welcome to the forum!

[QUOTE]Originally posted by Jack Sparrow:
The product of esterification using acid as catalyst seems pretty good. the FFA content is reduced to below 0.5.
How are you measuring FFA%

Hello Tilly,
Thank you very much for taking your time.

The method applied for FFA content analysis, is the American Oil Chemists'
Society (AOCS) method 5a-40. 1 g of sample was measured in a
conical flask and dissolve with 25 ml of isopropyl alcohol. The mixture
was then titrated with 0.1 N sodium hydroxide solution.

quote:

Most people would use around 6g- 7g NaOH to react a litre of WVO titrating around 1.
It would appear you are using too much NaOH in your reaction and producing excessive soap.


this info seems to be very helpful for my cause, thank you once again.
also during transesterification, i used 790 ml methanol for 1 liter esterified oil. is there standard amount to be used? or is there any method to figure out the amount of methanol to be used. what other precautions i need to follow in order to reduce saponification.

cheers, good day!
May 11, 2016, 11:39 AM
Tilly
Hi Jack,

quote:
Originally posted by Jack Sparrow:
this info seems to be very helpful for my cause, thank you once again.
also during transesterification, i used 790 ml methanol for 1 liter esterified oil. is there standard amount to be used? or is there any method to figure out the amount of methanol to be used. what other precautions i need to follow in order to reduce saponification.
cheers, good day!
Assuming your reactor is of adequate design, If you want to make very high conversion biodiesel using a single stage transesterification reaction, most people would use around 200ml methanol and 5g+ titration NaOH per litre of WVO being reacted.
Increasing the Methanol to 250ml per litre of WVO will help insure very high conversion.
So if your WVO titrated 2 the NaOH amount would be 5g+2g= 7g NaOH mixed into 200ml methanol for each litre of WVO titrating 2 being reacted.

In your case, there will be some methanol remaining in the WVO from the esterification stage so a bit of experimentation in reducing the methanol content in the transesterification stage will likely indicate that you could use less than 200ml Methanol per litre WVO in the transesterification stage.

I have limited experience using Acid esterification and I do not know the procedure you are using.

To keep soponification to a minimum insure your WVO is dry, do not use excessive NaOH and use low titrating WVO in the transesterification stage.

This message has been edited. Last edited by: Tilly,






August 23, 2016, 06:34 PM
sean lawson
I have been looking for this kind of information, I don't know why I didn't think before, this is such a great forum full of people that know what their are talking about. I started to get more involve on Biodiesel since a friend of my sister introduce me. Now Im on my own, and I glad to be here.
August 23, 2016, 06:48 PM
Tilly
Hi Sean,

Welcome to the forum.






August 27, 2016, 07:04 PM
WesleyB
"Is there any method to figure out the amount of methanol to be used, what other precautions i need to follow in order to reduce saponification?" I know some of those answers. Figure out the average molecular weight of the free fatty acids present in your type of vegetable oil. You can find the percentage of different types of free fatty acids in your type of oil. Then multiply the percentage of the free fatty acid times the molecular weight of that specific fatty acid. Add up all the multiplication products that should account for the contents of close to 100% of the fatty acids present. That gives average molecular weight of free fatty acids present in that type of vegetable oil. Palm kernel flakes have a different average molecular weight than corn oil. I think I calculated the average molecular weight of corn oil as about 279 grams per mole. Then you subtract 1 and add the atomic weights of 3 oxygen atoms and 5 hydrogen atoms to the 278 grams per mole to get the average molecular weight of the triglycerides. Then you weigh the oil you have in grams. Then you divide the mass of the oil by the average molecular weight of the triglyceride to get the number of moles of triglyceride present. Then you multiply by three to get the theoretical, stoichiometric (on paper, actual amount) quantity , minimum amount of moles of methanol required to theoretically get a 100% reaction. Then multiply by 32 grams per mole to get the mass of methanol required, then divide by 0.7914 grams per milliliter to get the volume of dry methanol required to do a 100% stoichoimetric reaction. That was something like 12% , without finding my paperwork calculations on paper, for corn oil. But many organic chemistry reactions do not proceed 100% as many inorganic reactions do. There is something called equilibrium in an organic reaction. The recantants producing the products go forwards and backwards. Too much product can push the reaction backwards towards the starting materials, especially if water is one of the products in the reaction, as in the Fischer Esterification (acid esterification of free fatty acids). In the Fischer Esterification, the more reactants will push the reaction to the products side of the equation (to the right). In acid esterification, methanol plus free fatty acid with sulfuric acid as catalyst produces fatty acid methyl ester plus water. Water is a product in the acid esterification reaction. Too much water would push the reaction backwards, it would hydrolyse the biodiesel back to the starting materials, free fatty acid and methanol. Hydrolyse means adding water to a molecule like fatty acid ester. Also water reacts with and destroys the methoxide intermediate midpoint very reactive charged molecule that briefly exists that causes transesterification to occur from a triglyceride to biodiesel and glyceride. To increase your percentage of product in acid esterification and base transesterification the water content ought to be a minimum. Drying the used vegetable oil might be an option prior to beginning making biodiesel. Also saponification is minimized when there is no water present initially when proceeding to the caustic transesterification step of the process.
August 28, 2016, 02:32 PM
Ryan P.
Holy run-on paragraph, Batman.....

Needs some structure in that, darn-near impossible to read...
August 28, 2016, 04:17 PM
Paulus
quote:
water reacts with and destroys the methoxide intermediate midpoint very reactive charged molecule that briefly exists that causes transesterification


Haha, I got it!
August 28, 2016, 07:04 PM
Tilly
Hi Ryan P,

quote:
Originally posted by Ryan P.:
Holy run-on paragraph, Batman.....
Needs some structure in that, darn-near impossible to read...
I have mentioned that very problem to Wessley before.
One time I even "fixed" it up for him so that it was morereadable like this below

' "Is there any method to figure out the amount of methanol to be used, what other precautions i need to follow in order to reduce saponification?"
I know some of those answers.
Figure out the average molecular weight of the free fatty acids present in your type of vegetable oil. You can find the percentage of different types of free fatty acids in your type of oil.
Then multiply the percentage of the free fatty acid times the molecular weight of that specific fatty acid. Add up all the multiplication products that should account for the contents of close to 100% of the fatty acids present.
That gives average molecular weight of free fatty acids present in that type of vegetable oil.

Palm kernel flakes have a different average molecular weight than corn oil.
I think I calculated the average molecular weight of corn oil as about 279 grams per mole.
Then you subtract 1 and add the atomic weights of 3 oxygen atoms and 5 hydrogen atoms to the 278 grams per mole to get the average molecular weight of the triglycerides.
Then you weigh the oil you have in grams.
Then you divide the mass of the oil by the average molecular weight of the triglyceride to get the number of moles of triglyceride present.
Then you multiply by three to get the theoretical, stoichiometric (on paper, actual amount) quantity , minimum amount of moles of methanol required to theoretically get a 100% reaction.
Then multiply by 32 grams per mole to get the mass of methanol required, then divide by 0.7914 grams per milliliter to get the volume of dry methanol required to do a 100% stoichoimetric reaction.
That was something like 12% , without finding my paperwork calculations on paper, for corn oil.

But many organic chemistry reactions do not proceed 100% as many inorganic reactions do. There is something called equilibrium in an organic reaction. The recantants producing the products go forwards and backwards.
Too much product can push the reaction backwards towards the starting materials, especially if water is one of the products in the reaction, as in the Fischer Esterification (acid esterification of free fatty acids).
In the Fischer Esterification, the more reactants will push the reaction to the products side of the equation (to the right).

In acid esterification, methanol plus free fatty acid with sulfuric acid as catalyst produces fatty acid methyl ester plus water. Water is a product in the acid esterification reaction. Too much water would push the reaction backwards, it would hydrolyse the biodiesel back to the starting materials, free fatty acid and methanol.
Hydrolyse means adding water to a molecule like fatty acid ester. Also water reacts with and destroys the methoxide intermediate midpoint very reactive charged molecule that briefly exists that causes transesterification to occur from a triglyceride to biodiesel and glyceride.

To increase your percentage of product in acid esterification and base transesterification the water content ought to be a minimum.
Drying the used vegetable oil might be an option prior to beginning making biodiesel. Also saponification is minimized when there is no water present initially when proceeding to the caustic transesterification step of the process.'







August 28, 2016, 10:54 PM
WesleyB
Sorry about that. I probably could not pass university English courses taught by short pretty women professors who hate large men, but I made staight A's in college organic chemistry. Caustic reacts with dry methanol to produce methoxide . But water decomposes methoxide which causes transesterification to occur. I do not know how much methoxide is produced, maybe 1% of the methanol is methoxide during the reaction occurring. Water decomposes the reactive midpoint chemical that causes the reaction to proceed. And triglycerides plus caustic in the presence of water produces soap. So for best results a minimum amount of water will increase biodiesel product percentage and minimize soap production.