Dear friends;

Here is titration steps of glycerol;
1- I prepared 0,1 N H2SO4 solution
0,1 Mol H2SO4 98,8% = 0,1 mol H2SO4=9,808 gr/mol, 9,808 gr/2 is number of equiavalent number = 4,90 gr. 4,90*100/98 = 4,97 gr. H2SO4. V=M/D V=4,97/1,84 V= 2,70 ml for 1000 ml distilled water.
(1000 ml distilled water + 2,70 ml H2SO4 at 98,5 % strength)
2- 100 ml Isoproply Alcohol
3- add 0,55 gr. melted glycerol into beaker
4- and then 1 ml bromophenol blue
5- drop 6 ml 0,1 N H2SO4 solution.
color change turned blue into yellow at this point.
Calculation;
If soap of 0,55 gram glycerol is required to titrate 6 ml 0,1 N H2SO4 solution, what is required acid amount to crack 1000 gram glycerol
6x2,7/1002,7 = 0,0161 ml H2SO4, for 1000 gr. glycerol cracking for 1000X0,0161/0,55= 29,27 ml/1kg H2SO4.

I added 29,27 ml H2SO4 glycerol, I could not split the glycerol as three phase. I have to say that adding 29,27 ml H2SO4 did not change to PH 4,5. PH is still at around 6.

Am I doing something wrong?
any comments would be very appreciated.

erdem-ozcan,
I am not certain I understand exactly what you are trying to do here. Are you trying to determine how much sulfuric acid to add to glycerol byproduct from BD production in order to neutralize the base (NaOH or KOH)? Are you trying to reprocess the glycerol byproduct in order to recover the FFA's so that you can make BD or just clean up the glycerol for some other use?
If you want to determine the amount of sulfuric acid to reprocess the glycerol byproduct why not simply add in increments concentrated sulfuric to 250 ml melted glycerol byproduct until the pH reaches less than 3?

Dear Rick G;

After removal of methanol and then cracking of glycerol coctail of Biodiesel reaction by siplitting into three phase with mineral acid. (remember 1st-dark one acid oil+ester 2nd-transparent glycerine+3rd-salt of mineral acid) ; I am trying to establish the reaction as shown below:

60-70 C 1ST PHASE + 2ND PHASE
1-GLYCEROL COCTAIL+H2SO4 ========> ACİD OIL + GLYCERINE + SALT
0,5-1 hr.

1ST PHASE + 2ND PHASE 180 C
2-ACID OIL + CRUDE GLYCERINE <========>TRIGLYCERIDE + H2O
8-10 hr

So stociometrically, I must need to know minumum acid amount to neutralize excess catalyst and soap of glycerol from Biodiesel reaction.
bye for now

I'm not sure I understand fully. But here are a few suggestions from what I have done:
Use concentrated sulphuric acid, using dilute acid you are just adding water,
I have found that glycerol before and after acid addition will have about 15% methanol by weight,
Glycerol will split into glycerol +FFA/biodiesel below pH 7. K2SO4 will start to precpitate at about pH 9. Crude glycerol from my experience is about pH 10-11.

quote:

Originally posted by erdem_ozcan:
. . . adding 29,27 ml H2SO4 did not change to PH 4,5. PH is still at around 6.

Am I doing something wrong?
any comments would be very appreciated.

You want to reduce soap to FFA. Did you retitrate the glycerol to the Bromophenol blue end point after you added the acid? If yes, what was the result? If not, why not?

The term pH does not apply to non-aqueous compounds. Therefore, the value of pH=6 may be in error.

I think you should have added the 2.7 ml of H2SO4 to 997.3 ml of distilled water. That would have resulted in a true 0.1N solution. However, I don't think the slight difference between 1000 ml and 1002.7 ml made any real difference in your results. A slight error in the estimated density of the acid could create a similar error.

quote:

Originally posted by erdem_ozcan:
. . . 2nd-transparent glycerine. . .

In my experience I rarely see a clear, transparent glycerol layer.

The top layer, made up of FFA and unbound biodiesel, has a low viscosity and is usually very dark in color. If you look very close and use a bright light you caqn see the different layers, clearly defined.

Theoretically, the glycerol should be clear. I follow the procedure (except I use HCl acid instead of H2SO4) you have outlined and my glycerol is almost always very dark brown to black. However, it is very viscous compared to the FFA/BD layer.

The salt (mine is NaCL) settles to the bottom. However, the granular nature of the salt entraps a significant amount of glycerol so the salt layer has a color very close to that of glycerol. Also, a lot of the salt stays dissolved and suspended in the glycerol.

I have tried to filter the glycerol using activated carbon to remove/reduce the color with very little success.

Dear Producer;

I checked it out again the results by focusing on correction of density: I literally assumed that the density of H2SO4 density was 1,84 gr/ml but infact,I have learned from acid aeller that real density of it is 65 Baume coresponding to 1,81 gr/ml at 15,5 F. So 4,97/1,81 = 2,75 ml H2SO4. I think that 0,04 ml correcton would create mojor error for titration. I will make a test again with 2,75 ml H2SO4+ 997,25 ml disstilled water.

thank you very much.

Producer,

Have you tried putting your crude glycerine thru a mini centrifuge? Might be worth a try.

erdem

It seems from your earlier posts that you are trying to firstly produce free fatty acids from the soap and then make triglycerides from the FFA and glycerol.

This is not possible. If you use enough conc sulphuric to begin this I think you will dehydrate the glycerol to acrolein.

To do anything useful you need to separate the FFA which float to the surface after acidification, which is easily done with swimming pool acid, 32% HCl, and much safer to handle than conc sulphuric.

Having got the separated FFA, which will contain some biodiesel esters, you can add this to your next batch of veg oil and make biodiesel with it. As it contains FFA you will of course need to do an acid/base two stage reaction.