NaOH / KOH Catalysts and the Chemistry behind them.

[Ross.Dunmall]

Since you asked for it. Yes it says on the packet, also the manufacturer has to declare the exact contents and will have to perform quality analysis and control over batches.

Characteristics	Specifications of 90% KOH
Total Alkalinity as KOH	95% Max
KOH	90% Min
K2CO3	0.5% Max
KCl	0.015% Max
Fe	3ppm Max
NaOH	1% Max
Ni	5ppm Max

Looking at it yes it does contain K₂CO₃ But in such a minute amount that it won't really impact badly on the reaction.

[countrypaul]

I know I asked, but I sort of expected that the contents would add up close to 100%, yet the figures given are barely 92%, so what is the rest?

Intresting that it quotes TotalAlkalinity as KOH at 95%, not totally sure what that means, but surely it suggests that it should behave as 95% KOH for titration purposes?

I agree that the K2CO3 content is so low as to be irrelevant, but I'm curious as to what the rest is, Ca - would seem unlikely?

Paul

[nigelb]

Ross,

You are entirely correct about the calculation problems that occur if using 90% KOH, the base amount will need to be adjusted, but the titration value would be correct. Beware that the strength of solution used for titrating is normally 0.1% not 0.1M. Several begginers have fallen foul of that difference in the past and wondered why the results they were getting were so far out!

As to where the value of 3.5g/L came from - I'm sure that must be from an engineer trying things rather than a chemist working it out

Paul

I remember falling foul of that difference. I had access to 0.1N NaOH at work and used it thinking that I had the right solution for titrating WVO.  I used it for almost 12 months before a chance posting on the VOD was picked up by countrypaul.  BTW...this was before the 3/27 was common knowledge.

Nige

[Ross.Dunmall]

Yeah very true. it could be upto 95% or even more KOH in purity. I somehow doubt this as then they'd only sell it at the higher purity and charge more for it.

It could also contain a few other chemicals leached in the electrolysis process. I'm pretty sure that it will be very well dried so as not to contain water. As the reaction of water with KOH is severly exothermic and would present too many hazard for storage and transportation.
 

[Ross.Dunmall]

I remember falling foul of that difference. I had access to 0.1N NaOH at work and used it thinking that I had the right solution for titrating WVO.  I used it for almost 12 months before a chance posting on the VOD was picked up by countrypaul.  BTW...this was before the 3/27 was common knowledge.

Nige

Did you soon learn to dilute the 0.1M solution, 1 Part 0.1M NaoH to 3 Parts Distilled Water?

As shown above o1M NaoH works out as 4g/l so add an extra 3l of water and suddenly it's 4g/4l or 1g/l

NOT THE SAME DILUTION FOR KOH THOUGH!!!

Infact for 0.1M KOH you'd need to Add an extra 4.6l of water to every 1l of 0.1M KOH to get 1g/l

[Ross.Dunmall]

I've been doing some drawing up of documents on Titration formulae and calculations, since it was such pain when I first started looking into it.

Take a look tell me what you think.

I don't know if the information will be helpful to others on here and I've got no experience in formatting information for wiki's, but if it's useful for the wiki and someone has the time to format it, then feel free to use it.

I've attached the file as both PDF and MS Word formats.

[attachment deleted by admin]

[Tony]

Thank you very much

[Ross.Dunmall]

Tony,

I've updated and re-uploaded the documents. I realized I forgot to add a paragraph right at the end explaining how to make the 1g/l solutions rather than the 0.1M (5.6g/l) Solutions.

[Tony]

OK, thanks - hopefully I'll have some time coming up to do something useful with those

[Julian]

Good stuff, Ross.  I've read it several times and keep getting that wooshing sound somewhere above my head.

I think it would be a great addition to the wiki, but as the wiki is primarily aimed at home producers (hopefully pages like this may broaden it's scope), I feel that a more basic explanation of the various calculations and formulae may be of benefit to most readers and muppets like me.

Tony, I had a look at wikiising formula when I did the venturi page.  Sub and super script are quite easy, but for things like two line heights within brackets, it seems to get very complicated.  Instead I opted for a graphic.  If that makes the page easer to compile, I'm happy to put the graphic together for you.

[Ross.Dunmall]

Yeah no problem Julian.

I can understand that maybe I took a slightly scientific approach to it, I have tried to make it simple, readable and understadable, but somethings either don't translate well to laymans or get lost in translation

In response to pulling the formula out as pics. If you open the file in Microsoft word you can select the formula and then copy paste as a pic.

[Ross.Dunmall]

I remember falling foul of that difference. I had access to 0.1N NaOH at work and used it thinking that I had the right solution for titrating WVO.  I used it for almost 12 months before a chance posting on the VOD was picked up by countrypaul.  BTW...this was before the 3/27 was common knowledge.

Nige

So interesting development. We had a visit from someone running a medium sized bio-diesel plant, he came down to chat to us, see our plant and offer advice he's gained from his 7-8 years in the business.

He watched as we did our titration and then said he thought our titration solution looked a little weak. So we made a fresh batch to ensure it was at full strength and he then tested it with no oil and still thought it was too weak.

Turns out he's not been diluting the 0.1M NaOH solution he uses, so is running titration solution four times too strong, but using base value of 7g KOH, somehow seems to be "managing to make EN14214 Spec fuel". I've so far failed to work out if he actually is getting away with it, is cheating or just using the gift of the gab. But I ran some numbers using an excel spreadsheet testing out the KOH value worked out using a number of different (some plain incorrect formulas) and none were close enough to accurate results and correct chemically proved titration formula. Interesting but still stumping me unless he's adding too much catalyst and managing to filter out the excess soap, catalyst and glyc formed out after.

Any insightor views on it?

From my understanding of the chemistry, either

[Tony]

I've found that so long as no water is involved in the process, you can overdo the catalyst quite safely and then just gravity separate any excess soaps created out of the final product (once Methanol has been removed).  All you're doing in that case is taking a hit on yield and wasting catalyst.

However, add 5-7% water in (for so called prewash where Glycerol is still present, aggressively mixing the lot) and if there is too much catalyst present then the whole lot turns to jelly.  If there is only a little too much catalyst then the jelly doesn't form until the mix cools.

Interestingly, excess NaOH is far more prone to making jelly when water is added than KOH, which seems much more tolerant to overdosing.

However, it's not so simple with other variables to consider:

- mixing Methoxide from NaOH/KOH and Methanol creates some water in the first place
- Methanol stops jelly forming, so that depends on Methanol percentage present too

All good fun and games