How much NaOH ?

[DavidA]

There has always been some variation in how much caustic you should use as your starting point when making methoxide.

It seems to range from 4.5 to 5.5 Gram per liter+titration.

So how much do you use ?

[nigelb]

I use 5g/lt on stage one and calculate the unreacted oil via a 10/90 for stage 2. Titations for me, and many others, is a thing of the past.

[dgs]

Years ago the chemist Neutral found out that 3.5gms/litre was insufficient to yield high conversion biodiesel (even though many on our uk forums have posted that 3,5gms is sufficient)

Neutral found that the 'sweet spot' for new oil was more like 5gms.

[DavidA]

I tended to use 4.5 Gram + titration.  And 240 Ml Methanol/Litre.

[dgs]

I tended to use 4.5 Gram + titration.  And 240 Ml Methanol/Litre.

24% methanol! Wow, money to burn!

[Tony]

I use 16% methanol and usually two or three stage it depending on how the conversion is looking after stage 1.  With about 10g/KOH/litre because I never titrate any more and have nice dry oil.  The catalysts aren't the expensive part of the reaction, that's the methanol!

And methanol recovery gives enough back to do a whole batch every now and again, which is nice!

I used to mix up the methoxide fresh for every batch but now I mix up enough for 4 or 5 batches at a time, it keeps well enough in sealed containers (used some after 6 months with the pandemic and all, it was fine!)

[DavidA]

I tended to use 4.5 Gram + titration.  And 240 Ml Methanol/Litre.

24% methanol! Wow, money to burn!

I may bring it down to 20%.  Better to err on the high side than to finish up with a jelly.