Started my second 250 gallon batch this morning, my first batch titration went 12 to 6 koh using the .2 multiplier from dkennys formula, this week I found out my acid is 97% so this batch I used .18, this oil titrated 18 koh at the start and in 4.5 hours went to 3, this acid base thing is KICK ASS man.

great job..
way to use the noggin.

starting that high drain about 1/2 the amount of methanol use used..or until the drained stuff doesn't look watery. the titration should drop more.. be sure to mix before titrating.

-dkenny

OK, when you say drain about half the amount of methanol used, is that after settling for a while? Then turn to pump back on and mix and re titrate?

yep. I let it settle for a couple of hours.
then drain, remix and titrate. then the base stage.

-dkenny

Cool, I'll try that next time, it looks like it yeilded around 96% this time.

Hi dkenny,
On this thread you recommended dont drain. however in other threads you recommended not to. Does it mean for very high acid value of oil, i must drain half but for not so high, do not drain?
Im having problems with this batch using your formula.The starting acid value for the sample was 218.40. After 13.5 hours, the acid value dropped to 99.94. At this rate, acid value will drop to 3 in about 25 hours. However, After 45 hours of treatment, the acid value of acid oil is 57.02. It seems that the reaction is proceeding very slowly.
Do you recommend draining and adding methanol again? Thanks.

brain,
exactly..
i found that for titrations less than 14 KOH draining wasn't usefull.
for titration over 18 it most useful. typically a 4 point drop in titration after draining.

on really bad oil..my last 'bad' oil batch started at 42 KOH. I mixed for a LONG time, settle and drained. after this titration was 10. redid the acid stage, but only use 3.5 gallons of methanol( the amount I drained out), titration ended at 5. fine for base processing using KOH.

so it sound like you need to let it settle, drain, retitrate and decide if another acid stage is needed or proceed with the base stages.

-dkenny

Dkenny,
I'm esterifying acid oil which is the byproduct of the refining process thats why the acid value is really high. Im using sulfuric acid. Is your formula for potassium?Thanks.

Brain,
All I used for a caustic is KOH. interestingly the 0.2ml number is the same for NaOH as KOH..try it the numbers work out the same

1g NaOH = 1.4g KOH

also what are you considering a high acid value? I'm asking because in a previous post my highest KOH was 42..while that changed yesterday..its now 55KOH. but this batch is still in process.

-dkenny

Starting titration was 218.40.

WOW.

Brain,
I would suggest that you plan on multiple acid stages. you might need 3 or 4 stages.
stage 1. start with 60% methanol. use 218-100=118*0.2 for the mls of acid per liter. mix for 12 hrs or so. if you watch the titration when it stops dropping this stage is done. let it settle then drain about 1/2 of the initial methanol volume.

stage 2. mix and titrate - this time aim for 30 to 40.

stage 3 try to get it the rest of the way to something near 3.

then base process.

I wish I could help more but I have needed to work with oil that bad. the batch I'm working on at the moment started at 55. I trying the multiple acids from the start. so far from 55 to 20.

good luck

-dkenny

Comments are welcome from everyone.

Starting acid value of sample: 218.40
Added 130 mL sulfuric acid and 360 mL methanol at 50 degC

After 19 hours 30 minutes, acid value dropped to 95.68
Added 65 mL sulfuric acid and 180 mL methanol at 50 degC

After 45 hours, acid value dropped to 61.74

separated the solid precipitates from the liquid sample. Around 600 mL of precipitates were separated.

I again added 65 mL sulfuric acid and 180 mL methanol at 50 degC

After 49 hours of reaction, acid value dropped to 26.23

After 4 days of sitting, acid value of sample increased to 46.88.

I again added 65 mL of sulfuric acid and 180 mL of methanol at 60 degC. After a total of 54 hours of reaction, acid value dropped to 25.72

So far, I have added 325 mL of sulfuric acid and 900 mL of methanol with a total reaction time, so far, of 54 hours.

This is getting too costly.
The four day sitting mentioned was only due to lack of time in tending to it. What do you guys think about this? Thanks.

I think you have your own answer, it's not worth it, there is definately a cut off point where the cost and time and effort out weigh the benefit.

Was your starting oil dry? High acid oils tend to contain water and will 'use up' the sulfuric acid. (The sulfuric acid is not only the catalyst but the dehydrating agent and water is a determent to the reaction) Try heating to at least 130 C befor starting. Also run the acid batches as hot as possible. Sometimes in high acid runs you might see three layers. You could also remove that layer and hold to the base operation.

Cat123,
I did not do moisture test but in previous batches, it would not even titrate if moisture was .1% and above. So we used to heat at 150 deg C before we titrate again. In this one, it titrated the first try so we didnt bother to evaporate. Thanks for the input though.