Oil to Methoxide OR methoxide to Oil?

[Bio Popo Member Find all posts View Profile Close Bio Popo]

Hello,
Just curious - I know that generally you are to add the methoxide to oil, BUT when performing a bracket-type titration where you're working with 200mL of oil and 50mL of methoxide, is it still critical or could one get away with adding the oil to the methoxide?
Thanks Guys!

Dave

[joe Moderator Find all posts View Profile Close joe]

Re: Oil to Methoxide OR methoxide to Oil?

To be honest I wouldn't think it would matter. I think its just evolved that way. With mass production for example it would be far easier to add 200 litres of methoxide to 1000Lts of oil than the other way around.
Joe

[Tony From West Oz Vice Chairperson of WARFA Find all posts View Profile Close Tony From West Oz]

Re: Oil to Methoxide OR methoxide to Oil?

Hello,
Just curious - I know that generally you are to add the methoxide to oil, BUT when performing a bracket-type titration where you're working with 200mL of oil and 50mL of methoxide, is it still critical or could one get away with adding the oil to the methoxide?
Thanks Guys!

Dave

In chemical processes, they almost always add the more reactive component to the less reactive component. This avoids high concentrations of highly reactive caustic/methanol solution acting on a little oil as the oil is added.

As my Chem teeech said "You always orter add the acid to the worter"

I believe that you should ALWAYS add the methanol/caustic to the oil.
This will avoid excessive soap production.

[tillyfromparadise Senior Member Find all posts View Profile Close tillyfromparadise]

Re: Oil to Methoxide OR methoxide to Oil?

Ah yes, Bracket titrations.

One of the many meaningless procedures recommended on Journey to Forever.
How does one decide which of the bracket is the best, or if in fact any are even close to the standard you wish to achieve.

Tilly

[Bio Popo Member Find all posts View Profile Close Bio Popo]

Re: Oil to Methoxide OR methoxide to Oil?

Well, you can tell which amount of KOH was the 'best' by seeing which amount created the most glycerine. But you're right, that's fairly vague bc the titration amount could be on the extreme side of high or low. So I think this method is only good for oil that appears 'healthy' and would have a more 'normal' titration amount (2-3ml).
Do other people agree that this method of titration is useless? Or is it worthwhile?

[tillyfromparadise Senior Member Find all posts View Profile Close tillyfromparadise]

Re: Oil to Methoxide OR methoxide to Oil?

Hello Bio Popo
No, the amount of byproduct generated is not an indication of completion.
The more NaOH/KOH you use, the more byproduct you will make, specifically soap. Use enough and you will turn the whole batch of oil into byproduct.

Actually, my testing has shown that if you use identical oil and only vary the amount of NaOH used, the higher the completion, the lighter the biodiesel produced.
But this involves washing and drying the biodiesel and even then the colour difference is hard to detect unless there is a difference in completion of several %.
If you go to the trouble of washing and drying you might as well do a few viscosity tests and get some meaningful information.

Tilly

[Sauman Senior Member Find all posts View Profile Close Sauman]

Re: Oil to Methoxide OR methoxide to Oil?

Good Day every one,
I would like to share a few facts that might give everyone an insight in the reaction mechanism and results .
This is based on alkali catalysed reaction:

Desired Feed Stock compostion:

• Acid value <1.0
• Moisture = anhydrous
• Total Free glycerol < .020~0.20

Process Varialbles in Tranesterification :

• Reaction Temp
• Purity of Oil
• Catalyst
• mixing intensity
• ratio of oil to vegetable oil

Reaction Parameters:

• 60-70deg centigrade at atmospheric pressure
• 240deg at 9000kpa (In this process both esterification and transesterification takes place....used for commercial and bulk)

Ratio Of alcohol to oil:

• 6:1 W/W yeils about 98%

Catalyst:

• 0.5~1% yeilds 94%~99% methyl esters.

Reaction mechanism.This will explain why catlyst to oil.

Pre Step:OH- + R'OH=R'O(-ve) + H20 or
NAOR' =R'O(-ve) + Na(+ve)

Step 1.ROOCR1 +R'O(-ve) = R1-C-0R-OR'-0(-ve)
Step 2.R1-C-OR-OR-O(-ve) + HOR= R1-C-ROH(+ve)-OR'-O(-ve) + OR'(-ve)
STEP 3.R1-C-ROH(+ve)-OR'-O(-ve) =R1COOR' + HOR

Where ROH = DIGLYCERIDE
RI = LONG CHAIN ALKYL GROUP
R' = Short chain Alkyl Group
Compostion of Desired Product %W/W:

• mONOGLYCERIDES=0.8%
• diglycerides=0.20%
• triglycerides = 0.20%
• Methanol =0.30%
• Free Glycerol =0.03%

Adding oil to metho will cause the FFA to be saponified and a lot of soap will result.Also gumms will cause hindrance in the whole reaction mechanism.

Hope to have answered

Cheers

Sauman

[tillyfromparadise Senior Member Find all posts View Profile Close tillyfromparadise]

Re: Oil to Methoxide OR methoxide to Oil?

I had egg on toast for tea tonight.

Tilly

[Matt Senior Member Find all posts View Profile Close Matt]

Re: Oil to Methoxide OR methoxide to Oil?

Joe, how did you know that? Yes it certainly is!

Matt

With mass production for example it would be far easier to add 200 litres of methoxide to 1000Lts of oil than the other way around.
Joe

[joe Moderator Find all posts View Profile Close joe]

Re: Oil to Methoxide OR methoxide to Oil?

Joe, how did you know that? Yes it certainly is!

Matt

Just guessing. BTW is it dangerous to add water to cordial in light of all of this. I 'm starting to wonder now if I should add the cordial last.

J