How can I neutralise NaOh in glycerol phase with solid acid catalyst such as Amberlyst-15 or liquid acid such as H2SO4? and
How I predict the amount of NaOH in glycerol phase? May you help me? Thank you from now.

If you're going to use sulfuric acid or hydrochloric acid, you can just put a sample of glycerine into a beaker with some neutral isopropyl alcohol, add bromophenol blue indicator, and start adding acid (very small amounts) until the indicator changes color. I suggested using the isopropyl alcohol so that you can actually see the color change which might be difficult with dark glycerine alone- diluting it with alcohol may make it easier to see.

Afterwards, scale up the amount of acid used, to the size of batch you're actually going to neutralize. For example:
titrate 100 ml of glycerine by adding hydrochloric acid till bromophenol blue end point
multiply the amount of acid used by 10 so as to get the amount of acid needed to neutralize 1000 ml of the same glycerine.

The glycerine will split into at least two phases (probably two)- oils on top (biodiesel and free fatty acids from breaking up the soap in the glycerine) and all water-soluble substances including glycerine on the bottom. Both phases will be saturated with salts, I think (or maybe just the lower one is saturated with salts- I'm not sure).

You'll get slightly acidic glycerine at this point and if you need it to be neutral pH 7 for some reason you'd have to titrate it back to neutral with an alkali. I dont know what the best one to recommend is.

Anyone know the answer to that?

Mark

PLease note: I have not tried this direct titration with sulfuric acid so I dont know if itll work (I don't know if this is true, but perhaps if the sulfuric is too strong you may want to dilute it in water before titratng)

Thank you for your commends
Can I use phenolphtalein indicator for titration of glycerol to find NaOH amount in the glycerol phase?
If I would neutralise glycerol but it is still in i-propyl alcohol. I want to use NaOH free glycerol so I want to neutralise it. So what must I do?

Should be able to, but I haven't tried it.


what are you using the glycerol for, by the way?


Mark