The chemistry of the glycerol (and soap) phase

[WesleyB Donating Member Find all posts View Profile Close WesleyB]

Re: The chemistry of the glycerol (and soap) phase

Dr. Mark; The constant of acidity of methanol is given as 2.9 times ten to the minus 16 power. That's a pH measurement. Methanol is a weak acid as is ethanol. That's the equilibrium constant at standard temperature and pressure for methanol. That's the acid disassociation constant. The biggest problem I've run into is when a quantity of potassium hydroxide is dissolved in methanol the constant of basicity isn't in water as a dilute solution. There's about 10-15% water in solid potassium hydroxide. Then the formation of water when methoxide is produced, escorted by potassium ion. The pKa of methanol is 15.54, but that's in water. It seems to me that since a small amount of water is present the normal equation for calculating eqilibrium of bases (methoxide) doesn't work. I don't know how to calculate the amount of methoxide present in anhydrous methanol with potassium hydroxide dissolved in it. Then adding calcium oxide to the mix which absorbs or adsorbs most of the water present furhter complicates figuring the quantity of methoxide present. Remember using calcium oxide to dry ethanol only produces 99.5% dried ethanol it's not 100%.

[tillyfromparadise Senior Member Find all posts View Profile Close tillyfromparadise]

Re: The chemistry of the glycerol (and soap) phase

Hi Mark,

I give up. I can see now that it was a mistake to attempt to engage with you at all...and will just go back to ignoring everything you say.

Do you mean you will no longer tell me what an intelligent and well educated chap you are or that you think I am childish and do not understand the Chemistry. That is a great disappointment.

[Dr Mark Senior Member Find all posts View Profile Close Dr Mark]

Re: The chemistry of the glycerol (and soap) phase

Mark,
I did a quick Google and found (amongst others) http://www.arpnjournals.org/jeas/res..._0816_4863.pdf
This gives the Molar ratios and the reaction coefficients for different reaction temperatures.
Now, this should give us the ability to predict the amount of water for the given ratios of KOH and MeOH.
I believe that Molar ratios are based on the relative mass of the feedstock eg KOH should have K (40), O (16), H (1) = 57, Methanol CH3OH would have C (12) H *4 (4) O (16) = 32
In this case a molar ratio of 0.012 ( KOH:MeOH) would give mass ratios of (32*0.012):57 or 0.0067. Thus for a molar ratio of 0.012 KOH:MeOH you would need to add 6.7g of KOH per Kg of Methanol.

For a reaction temperature of 25° and a molar ratio of 0.012, this would give us:
KOH in solution 1.09%
CH3OH in solution 96.91%
CH3OK in solution 1.64%
H2O in solution 0.81%

Are my figures accurate?

Please comment on this as I have only lower school Chemistry.

Right, let's have a look at this. I'm not sure where you got those numbers from, but we can work through this one step at a time.

As it happens it proves everything I've been saying, but it's nice to have some actual numbers to work with.

I've attempted to insert some images from the paper, however, which are cut and pastes of the relevant charts and figures, but when I use the Insert Image function it says it is an invalid file, despite the fact that I've tried both jpg and png formats. What am I missing?

[Dr Mark Senior Member Find all posts View Profile Close Dr Mark]

Re: The chemistry of the glycerol (and soap) phase

Dr. Mark; The constant of acidity of methanol is given as 2.9 times ten to the minus 16 power. That's a pH measurement. Methanol is a weak acid as is ethanol. That's the equilibrium constant at standard temperature and pressure for methanol. That's the acid disassociation constant. The biggest problem I've run into is when a quantity of potassium hydroxide is dissolved in methanol the constant of basicity isn't in water as a dilute solution. There's about 10-15% water in solid potassium hydroxide. Then the formation of water when methoxide is produced, escorted by potassium ion. The pKa of methanol is 15.54, but that's in water. It seems to me that since a small amount of water is present the normal equation for calculating eqilibrium of bases (methoxide) doesn't work. I don't know how to calculate the amount of methoxide present in anhydrous methanol with potassium hydroxide dissolved in it. Then adding calcium oxide to the mix which absorbs or adsorbs most of the water present furhter complicates figuring the quantity of methoxide present. Remember using calcium oxide to dry ethanol only produces 99.5% dried ethanol it's not 100%.

The paper that Tony sent me contains some very useful data. I'll give a fuller explanation, now that I have some real numbers, as soon as I can figure out how to cut and paste figures from the paper. I saved them as jpg screen captures but for some reason they won't upload

Wasn't aware of the 99.5% figure for ethanolic dehydration. Where did you get that from? I know for a fact that when organic chemists want to dehydrate an alcohol of any sort they use CaO - nothing works better. But 99.5% is probably good enough anyway. Although I now use cement, not CaO, which has other anhydrous compounds in there.

Trying to make theoretical predictions in situations like this based on pKas is fraught with danger, for exactly the reasons you cite - different solvents, hydrogen bonding etc.
T

[WesleyB Donating Member Find all posts View Profile Close WesleyB]

Re: The chemistry of the glycerol (and soap) phase

My reference to drying ethanol is from "A Text-Book of Practical Organic Chemistry" author Arthur I. Vogel , publisher Longman Group Limited , Third Edition, pages 166-167 in the article titled Absolute Ethyl Alcohol. "The product is generally termed "absolute" ethyl alcohol, although it usually still contains about 0.5 per cent of water." In the book the next proceedure is for "super-dry" ethyl alcohol where magnesium metal and iodine then anhydrous distillation is used to further dry grain alcohol to 200 proof. It seems to me that calcium oxide with slighty wet alcohol still has an equilibrium where the ethanol is not perfectly dried.

[tillyfromparadise Senior Member Find all posts View Profile Close tillyfromparadise]

Re: The chemistry of the glycerol (and soap) phase

Hi Mark,

...and have deluded yourself into thinking that you understand some chemistry just because you have learned a few big words,...

Big words?
I didn't think I was using big words.
Which words that I use do you classify as "big Words"?

[Dr Mark Senior Member Find all posts View Profile Close Dr Mark]

Re: The chemistry of the glycerol (and soap) phase

The paper that Tony sent me contains some very useful data. I'll give a fuller explanation, now that I have some real numbers, as soon as I can figure out how to cut and paste figures from the paper. I saved them as jpg screen captures but for some reason they won't upload

Wasn't aware of the 99.5% figure for ethanolic dehydration. Where did you get that from? I know for a fact that when organic chemists want to dehydrate an alcohol of any sort they use CaO - nothing works better. But 99.5% is probably good enough anyway. Although I now use cement, not CaO, which has other anhydrous compounds in there.

Trying to make theoretical predictions in situations like this based on pKas is fraught with danger, for exactly the reasons you cite - different solvents, hydrogen bonding etc.
T

Can anyone tell me how to insert jpg or png figures into a post please? I can't continue this discussion without using some of the figures from the paper that Tony sent me, but every time I try to paste them it says "wrong file format."

One more thing. As I've never used the Dr Pepper method I've no idea what quantities are used. If someone can give me a typical amount of KOH or NaOH that is used to make the methoxide solution I'll use the data in the paper that Tony sent me to calculate how much water you are adding to your mixture when you use the Dr Pepper method

[tillyfromparadise Senior Member Find all posts View Profile Close tillyfromparadise]

Re: The chemistry of the glycerol (and soap) phase

Hi Mark,

One more thing. As I've never used the Dr Pepper method I've no idea what quantities are used. If someone can give me a typical amount of KOH or NaOH that is used to make the methoxide solution...

Do you really mean that you have no idea how to find out the Quantities used in the World Famous Dr Pepper Technique (Pat Pend)

HINT: There is a sticky at the top of the Making Biodiesel Forum titled "World Famous Dr Pepper Technique (Pat pend)". If I were a betting man, I would bet that you can find all the quantities that you require mentioned there.
Unfortunately there are a few big words in the thread. If you have any problem understanding anything please feel free to ask for help.

[Dr Mark Senior Member Find all posts View Profile Close Dr Mark]

Re: The chemistry of the glycerol (and soap) phase

Please note:

This is the only room temperature method on the web.

The Dr Pepper method has two heating steps:

1. Heating of WVO to "dry" it
2. Heating the biodiesel mixture to facilitate the transesterification process.

This method requires no heating at any stage

[Qwarla Senior Member Find all posts View Profile Close Qwarla]

Re: The chemistry of the glycerol (and soap) phase

The Dr Pepper method has two heating steps:

1. Heating of WVO to "dry" it
2. Heating the biodiesel mixture to facilitate the transesterification process.

You are wrong Mark or do you find pleasure in peddling misinformation?

1 heating step, then
1 cooling step.

Go and actually read the instructions before having a hissy fit.

MAKING THE BIODIESEL!
When the Oil's temp has dropped to 55 deg c or a bit less, using a funnel, pour the litre of oil into a DRY 2 litre Dr Pepper bottle (in a pinch any other brand of bottle will do).
Pour the methoxide on top of the oil using the same funnel.

[Dr Mark Senior Member Find all posts View Profile Close Dr Mark]

Re: The chemistry of the glycerol (and soap) phase

You are wrong Mark or do you find pleasure in peddling misinformation?

1 heating step, then
1 cooling step.

Go and actually read the instructions before having a hissy fit.

MAKING THE BIODIESEL!
When the Oil's temp has dropped to 55 deg c or a bit less, using a funnel, pour the litre of oil into a DRY 2 litre Dr Pepper bottle (in a pinch any other brand of bottle will do).
Pour the methoxide on top of the oil using the same funnel.

I really don't understand why this is so difficult to understand. You've just told me with the Dr Pepper the oil has to be "heated" and then cooled to 55 degrees. I know it does. That's my point. My method was developed to eliminate the heating steps

Don't you understand what I'm saying. The oil with my method never needs heating. Not having a hissy fit. Just stating a fact.

The oil with my method does not have to be heated to be dried, and the reaction proceeds at room temperature.

I do not own a heater, as I do not need one, ever.

You don't need to spend money on a reactor vessel with a heater. You can make the batch in whatever you want. I use a plastic IBC, and make 1000L at a time.

[tillyfromparadise Senior Member Find all posts View Profile Close tillyfromparadise]

Re: The chemistry of the glycerol (and soap) phase

Hi Mark,

Please note:
This is the only room temperature method on the web.

Of course it is not. There are many room temperature methods of making biodiesel on the web.
Surely you have heard about the method that makes biodiesel at room temperature using Fungi
https://www.wired.com/2007/08/fungi-make-biod/

And of course there is the room temperature method that uses egg shells as a catalyst. Everyone knows about this method.
https://www.sciencedirect.com/scienc...16236116303933

There is also everyone's favourite Room temperature method that uses coconut husk ash as a ctalyst. I can not believe you have never heard of this method. It is all the rage.
https://www.sciencedirect.com/scienc...60544214004587

And many others too numerous to list


By the way, you have not yet reminded everyone today that you have two degrees in Chemistry.

[Dr Mark Senior Member Find all posts View Profile Close Dr Mark]

Re: The chemistry of the glycerol (and soap) phase

Please note: my method is the only room temperature method on the web.

It does not require heating at any stage.

Note that you can watch videos of the process on my website here. There is an in-reactor temperature probe to measure the temperature

[tillyfromparadise Senior Member Find all posts View Profile Close tillyfromparadise]

Re: The chemistry of the glycerol (and soap) phase

Hi Mark

Please note: my method is the only room temperature method on the web.

Surely it is not. Your procedure is only one of many room temperature methods on the internet.
Besides the room temperature methods I listed above there is also the "Production of biodiesel at room temperature from palm olein oil"
https://www.researchgate.net/publica...palm_olein_oil

Of course there is also Room-Temperature Conversion of Soybean Oil and Poultry Fat to Biodiesel Catalyzed by Nanocrystalline Calcium Oxides
https://pubs.acs.org/doi/abs/10.1021/ef050435d

Do not forget Room Temperature synthesis of biodiesel using sulfonated graphitic carbon nitride
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5172360/

PS, I really think people are waiting for you to tell them that you have two degrees in chemistry

[Dr Mark Senior Member Find all posts View Profile Close Dr Mark]

Re: The chemistry of the glycerol (and soap) phase

Mark,
I did a quick Google and found (amongst others) http://www.arpnjournals.org/jeas/res..._0816_4863.pdf
This gives the Molar ratios and the reaction coefficients for different reaction temperatures.
Now, this should give us the ability to predict the amount of water for the given ratios of KOH and MeOH.
I believe that Molar ratios are based on the relative mass of the feedstock eg KOH should have K (40), O (16), H (1) = 57, Methanol CH3OH would have C (12) H *4 (4) O (16) = 32
In this case a molar ratio of 0.012 ( KOH:MeOH) would give mass ratios of (32*0.012):57 or 0.0067. Thus for a molar ratio of 0.012 KOH:MeOH you would need to add 6.7g of KOH per Kg of Methanol.

For a reaction temperature of 25° and a molar ratio of 0.012, this would give us:
KOH in solution 1.09%
CH3OH in solution 96.91%
CH3OK in solution 1.64%
H2O in solution 0.81%

Are my figures accurate?

Please comment on this as I have only lower school Chemistry.

Tony I've just set up a photohosting account at imjur. But no matter what I do it won't let me post an image.

I post the images to the account and then cut and paste the URL but it keeps saying Invalid File