Two stage no tit-question

[Rossey]

I want to try the above as I still don't quite understand titrations.

So to make sure I've got it right.

I will have a 100l batch

So I measure out 3.5g per litre (naoh) = 350g with 80% meth = 16l

But this bit I don't quite get.

2nd stage

How much Noah do I add?
Is it only the amount of drop out in my 90/10 with the remaining 20% of meth?


And can someone clarify how I go about reading and working out 'drop out' from a 90/10 flask please.

[julianf]

S1 chem is open to debate - people do different things here, but your figures dont look crazy.  Personally, id add more catalyst, but many dont.

S2 -

the drop out in ml that you read on a 10/90 test is related to the percentage unconverted (in the whole batch)

so, if you add 10ml of product, and you get 1ml drop out, then that is 10% of the 10ml - which also means 10% of the batch as a whole.

so, say, you get 0.8ml drop out on a 10/90 test, and you have 95 litres in the reactor after dropping the glycerol, then that is...

0.8ml is 8% of 10ml
so 8% of the batch unconverted
so 8% of 95litres is...

95 x 0.08

(whatever that is!)

so then you have your liters of oil left in the batch

you then need to mix up the chem for that (not for the whole batch!)

again, open for debate as for the quantity, but, with naoh, 5g / ltr (of unconverted) + 20% of meth (again of the unconverted) would not be far out.

test again at the end of s2, to be sure.

[Chug]

If you have say 1ml dropout in 10/90, that is 10% unconverted oil so you need to add 10% of the original amount of catalyst to the remaining 20% Meth.

so if the original catalyst amount was 350g then it's 35g NaOH in 4 litres meth.

Unless the oil is little used you will probably get more than 1ml fallout using only 350g NaOH, but it just means adding more catalyst for stage 2, after a few batches you will have a handle on the amounts your oil needs.

A tip from me, when you think you have finished take a sample from your processor before you turn everything off and leave it to settle, if you have any problems with glyc not separating or jellying bio you will find out before you start to settle/drain the main batch and can try and fix it rather than leaving it to settle the glyc and finding out later when you come to drain the main batch.

[Rossey]

Thanks guys 

What temperature do I react at?
And meth boils at 64c doesn't it?

[willbuild]

A good question, I think it starts at 67c , I also wander is there an exact temp to process at. I start at about 58c switch off the heating element so that its still above 53c by the time 2nd stage is done.

[therecklessengineer]

Reaction temperature isn't really that critical. Somewhere between 50-65 will be fine.

[nigelb]

I know of people who react in the 70's.

The thing with methanols boiling point is that it only relates to it as a stand alone and pure liquid. Once you mix it with hydroxides or methylates and WVO the boiling point has little relevance to 65C. When blended all sorts of properties change.

[Julian]

I know of people who react in the 70's.

The thing with methanols boiling point is that it only relates to it as a stand alone and pure liquid. Once you mix it with hydroxides or methylates and WVO the boiling point has little relevance to 65C. When blended all sorts of properties change.

I often react at over 70°C.

Methanol must vapourise from the mix or you wouldn't be able to distill it off.  My take is that as a GL is 'effectively' a sealed system bar filling, emptying, expansion and contraction, the ullage space will be saturated with vapour, leaving the bulk of the methanol in the mix.

Some vapour will obviously condense on the processor walls and run back into the mix, to be replaced by newly evolved vapour.

Whatever process the methanol undergoes, the reaction still occurs.  Wether it occurs any quicker is difficult to say, but it certainly speeds up my demething which was previously sluggish to say the least.

[nigelb]

I dare say that methanol begins to vapourise at very low temperatures. A bit like water really...starts to vapourise way before boiling point

[Jamesrl]

I often react at over 70°C.

Methanol must vapourise from the mix or you wouldn't be able to distill it off.  My take is that as a GL is 'effectively' a sealed system bar filling, emptying, expansion and contraction, the ullage space will be saturated with vapour, leaving the bulk of the methanol in the mix.

Some vapour will obviously condense on the processor walls and run back into the mix, to be replaced by newly evolved vapour.

Whatever process the methanol undergoes, the reaction still occurs.  Wether it occurs any quicker is difficult to say, but it certainly speeds up my demething which was previously sluggish to say the least.

You're absolutely correct, once the head space is saturated there's nowhere for any more methanol to evaporate too.

I react the first stage at 65c, it's also the temperature I inject the methoxide.

During the second stage I increase the temperature to 80c ready to go straight into demeth.

[Jamesrl]

I dare say that methanol begins to vapourise at very low temperatures. A bit like water really...starts to vapourise way before boiling point

Correct, methanol starts to evaporate at -97.999c so I don't know why peeps are so concerned with the boiling point of 64.7c.

[nigelb]

I dare say that methanol begins to vapourise at very low temperatures. A bit like water really...starts to vapourise way before boiling point

Correct, methanol starts to evaporate at -97.999c so I don't know why peeps are so concerned with the boiling point of 64.7c.

'cause  for some, that's the only information they have about the stuff and often quote it unnecessarily. A little knowledge is a dangerous thing.

[Rossey]

I dare say that methanol begins to vapourise at very low temperatures. A bit like water really...starts to vapourise way before boiling point

Correct, methanol starts to evaporate at -97.999c so I don't know why peeps are so concerned with the boiling point of 64.7c.

Because I don't want a kaboom 

[Rossey]

I dare say that methanol begins to vapourise at very low temperatures. A bit like water really...starts to vapourise way before boiling point

Correct, methanol starts to evaporate at -97.999c so I don't know why peeps are so concerned with the boiling point of 64.7c.

'cause  for some, that's the only information they have about the stuff and often quote it unnecessarily. A little knowledge is a dangerous thing.

It's all new to me and that's why I'm asking the questions 

[nigelb]

There are some things, chemically, you don't need to be concerned about Rossey. However, I think that plant design and adequate ventilation should be top of your list.

Good practice with chems is something to take note of with good PPE and ventillation so as not to come in contact with fumes or liberated dust.

I wasn't trying to be patronising..sorry if it came across like that.

Questions are good...especially when relevant.