Shelf Life of Methoxide?

[Aussie1 Biofuels Forum Newbie Find all posts View Profile Close Aussie1]

Can anyone tell me if methoxide has a shelf life? It would be stored in an air tight container out of sunlight and in a reasonbly cool place. At this stage I will only be making small quantities of Biodiesel and I would prefer to make up a larger batch of methoxide and use it as required. Thanks.

[Terry Syd Senior Member Find all posts View Profile Close Terry Syd]

Re: Shelf Life of Methoxide?

Both methanol and the NaOH or KOH are hydroscopic, which means then suck up the moisture big time if you give them a chance. However, if you keep the container closed from the atmosphere you prevent the moisture from getting to the methoxide.

In the early days, it was one of those urban myths that you had to 'fresh' methoxide for a batch.

I have used methoxide that has been stored for more than six months. It worked just fine.

[Tony From West Oz Vice Chairperson of WARFA Find all posts View Profile Close Tony From West Oz]

Re: Shelf Life of Methoxide?

In the past, I have proposed the use of a concentrate methanol / caustic solution which could be diluted to suit the titration of a particular batch of oil. This means that the concentrate could be made to a standard g/l ratio which is, for example, twice the concentration required by the worst oil you have access to (perhaps 100 g per litre of Methanol).
I do not know if this concentration is possible, but this is an example only.

If you titrate an oil at 5 g/l. With a catalyst amount of 5g/l, you need 10 g/l NaOH (w/vol oil). If using a 20% v/v methanol, you would require to use 100ml of the concentrate (giving 100g NaOH) and 100ml of methanol per litre of the batch, (giving a total of 200 ml methanol.)

As liquid measures are simpler than weight measures for many home brewers, thie would be an easy process, to be done art leisure. Making up a concentrate based on the package size of the NaOH would eliminate the weighing process and provide a "bulk" amount of the concentrate, to be diluted depending on the titration and batch size.

Providing that the concentrate and methanol were kept in sealed containers and labelled accordingly, I see no additional hazards or issues for the user.

Your comments would be appreciated.
Tony

ps. A question for the chemists amongst us: How much NaOH can dissolve in a litre of Methanol?

[Aussie1 Biofuels Forum Newbie Find all posts View Profile Close Aussie1]

Re: Shelf Life of Methoxide?

Thanks Terry & Tony. I have access to a lab with three chemists, fume cupboard various scales and equipment so will make up batches there. I'll keep that in mind Tony regarding the concentrate as I may not have access to the lab etc for ever. I'll also keep watch for the replies from the chemists.