Methanol concentrate in the tails according an EC study

[mark_m]

I realize this topic has been exhaustively argued, but I only saw this topic yesterday, and so I want to see if I can set the record straight concerning this EU study with respect to some misconceptions about methanol behavior, so I have attached a PDF with my research on this topic.

Ethanol-Methanol Curves.pdf

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[Hügelwilli]

This is BS. Of course the methanol amount has to be divided by the ethanol or otherwise to compare them.

The results purport to show that methanol increases in concentration not in the first cut of the pot-still distillation, but in the tails, in direct conflict with common knowledge and boiling-point profiles for methanol and ethanol. This so-called behavior is apparently seen in figure 3 of the paper. To demonstrate that this figure is completely misleading, not significant, and that methanol behaves according to common sense and intuition,

Your call it common sense and intuition, I call it BS.
If you would research deeper you would find many substances with boiling points way over 100°C which are accumulating in the heads. Boiling points say nothing about how the volatile the substance is dependent on the ethanol concentration.

[mark_m]

There's no useful information in comparing ethanol and methanol concentrations with respect to each other. All that matters is their concentrations with respect to the final product. With respect to boiling points, all I pointed out is that without knowing anything about azeotropes and/or hydrogen bonding from molecular polarity, you would EXPECT the lower BP phase to vaporize before the higher BP phase (most people subscribe to this) and that the study made a big point about how this conflicted with their bogus figure 3. That's it.

[Hügelwilli]

https://en.wikipedia.org/wiki/Relative_volatility
Relative volatility is a measure comparing the vapor pressures of the components in a liquid mixture of chemicals. This quantity is widely used in designing large industrial distillation processes.[1][2][3] In effect, it indicates the ease or difficulty of using distillation to separate the more volatile components from the less volatile components in a mixture.
You see the word "relative"? This is the key. You have to see the relative values to ethanol to see if something separates and where it separates. You need the relative volatility in dependence of the varying ethanol concentrations. Man, there are dozens of studies with relative volatilities in spirits. All have this topic: To find out when and at what conditions which congener comes over more or less. Simply try to find some. All agree, that methanol is more a tails than a heads problem.

If you have a fraction with 80%abv and 0.1% methanol and a second with 40%abv and 0.08% methanol, what does this mean? Yes the first fraction has more methanol. But when you dilute the first fraction to drinking strength 40%abv, voila now there is less methanol in the first fraction. And like you wrote : "All that matters is their concentrations with respect to the final product." That's it. Although the first fraction has more methanol in absolute terms, it hast less methanol in relative terms. And this is all that matters if we dilute to a certain abv.

Aceotropes have nothing to do with volatility. At least if we are dealing with very low concentrations. And when we are discussing about methanol or other congeners, we have low concentrations.

[mark_m]

Wow! Have you won your case?

[Sporacle]

I don't think many people have argued about methanol concentrations.
I believe that most people here are of the opinion that methanol is present throughout the run.
Never given to much thought as to the concentrations throughout the run and as I mainly do rum and grains.
Good luck

[shadylane]

Here's a link.
viewtopic.php?t=40606

[kennstminet]

It seems that I do not clearly understand what @mark_m stated.
If anyone wants to read the 168 pages carefully, here is a link to the study document.
https://op.europa.eu/en/publication-det ... b6abc1aa37

I see no information that methanol would concentrate in the tails.
It says that methanol content increases in a final product when tails are recycled rather than thrown it away.

[Hügelwilli]

A quote from the study:

The investigation shows that there is in g/hl p.a. an increase of methanol contents during the distillation and especially in the last fractions (tailings). This is caused by the fact that methanol is, in spite of the lower boiling point (64,8 °C) compared to ethanol (78,3 °C), carried over in the distillate later than ethanol, an observation that is also confirmed by former investigations and in the literature.

And later they say that the difference between heads hearts and tails is not much and there is not much you can do.

And later you can see measurement curves that show how the methanol rises during the run relative to ethanol.

And by the way there are lists with measurements results also from many other congeners. There you could search for foreshot substances and google their boiling points. Some values will surprise the people who think boiling points of pure substances have a meaning for volatility in distillation of spirits. For example methyl palmitate page 42 line 6 distills over early but has a boiling point of freaking 417°C.


But of course, if you don't like those results you still can do it like Bolverk here:
viewtopic.php?p=7696483#p7696483

Oh, and who funded the studies: the European Commission.
How much money do they have: 148 billion euros yearly budget.

[Renhoekk]

Could you elaborate on “methanol behaves according to common sense and intuition”?

[Bolverk]

But of course, if you don't like those results you still can do it like Bolverk here:
viewtopic.php?p=7696483#p7696483

Oh, and who funded the studies: the European Commission.
How much money do they have: 148 billion euros yearly budget.

Berserk said that, not me

[kennstminet]

It seems that I do not clearly understand what @mark_m stated.

It seems that I need to apologize. I had not read everything.
Mark_m's statements are hidden in the pdf he had posted, rather than in any post's text.
Now, after heaving read what is written there, I tend to agree that mark_m is entirely wrong with his reasoning and conclusions.

[Hügelwilli]

I am sorry Bolverk. Of course it was not you.

[mark_m]

Could you elaborate on “methanol behaves according to common sense and intuition”?

I simply state that to most people who have not read this EU report (or even if they have!) or some similar report they expect that methanol behaves like ethanol to the extent that it comes out with most concentration early and diminishes throught the run. I don't think common sense and intuition would lead you to believe that methanol is mostly in the tails (as fig. 3 would lead you to believe).

[kennstminet]

mark_m

Lets look at Figure 3 for distillation 4, indicated by open circles.
Distillation 4 is a single Potstill Distillation with 130 L of 5,7%abv mash in the boiler. A total of 30 Liters is collected in 20 fractions jars of 1,5 L content.
The measured values are shown in table 3a.
Figure 3 shows Methanol relative content as ml Methanol per 100 ml pure ethanol for each individual fraction.
This makes sense. If you know that a certain fraction with 47%abv has 1,08 ml Methanol per 100ml pure Ethanol, it is easy to calculate the Methanol content after dilution or for larger amounts of distillate.

I took the raw numbers from table 3a and made my own graphs.
It can easily be seen that the relative Methanol content slowly increases from the start of distillation. Starting at 0.99 ml/100mlEth, the relative Methanol content increases slowly to 1,79 ml/100mlEth. This is fraction jar 10 and the %abv in this jar has already decreased to 18,4%abv.
The next 10 jars are usually not used anymore by a homedistiller.
At fraction jar 15, the %abv are down to 6,5% while the relative Methanol content has increased to 2,78 ml/100mlEth.
Fraction jars 16 to 20 Ethanol content further decreases down to 2,1%abv in jar 20. From jar 16 to 20 the relative Methanol content increase gets steeper. This is caused by the fact that that the Ethanol content in the boiler approaches zero while there is still Methanol in the boiler to distill.

The measured data clearly shows a slow increase of relative methanol content from jar to jar for this potstill single distillation in the range of distillate %abv a homedistiller would consider to use as product.

Here are my graphs of the data from table 3a.
The first one shows the %abv in each fraction jar and its relative Methanol content as ml/100mlpure Ethanol

The next on shows the relative Methanol content in ml/100mlpure Ethanol versus the %abv of each individual fraction jar.

[mark_m]

Kennstminet,

I agree with everything you have produced and stated here. I reproduced the same curves and arrived at the same conclusions as you. But we are viewing these data from two different viewpoints. If you are from a technical background and understand basic math and unit conversion, the data say one thing. If you are not from a technical background you are left with a different perspective on these graphs. I am a retired geophysicist, so I get what you are saying, but let me try to clean up the mess I've made with more clarity of my main points.

1. I believe it is fair to say that there is an overwhelmingly popular myth among many home distillers that the lower boiling point of methanol (as opposed to ethanol) is enough to surmise that the methanol will either entirely or largely be in the earliest arrivals and persist until ethanol boiling temperature is reached, when it is gone. Given the fact that there is little but anecdotal evidence to the contrary, I believe that the EU study does a good job of debunking this idea by showing on fig. 2 that methanol is much more stubborn than ethanol in remaining in the boiler.

2. I agree with the point that the study does a good job of pointing out that the practice of recycling tails (particularly of fruit brandies) is probably not a good idea. They have attempted to show this with figure 3 by showing that methanol is, in fact, increasing in relative concentration as the ethanol peters out. But, in doing so, they have produced a graph which leads many to believe, contrary to what they always believed, the methanol doesn't come out in the fore shots, and is somehow pushed into the tails. They look at the scale and think, "goodness, there is up to 4% methanol in the tails of my distillate. Now, I know that the expert and well-heeled distillers in this forum know better than this and scoff at the less-informed that interprets this graph this way, but you must admit that there is damn little published information that explains this whole methanol mess in a clear and concise fashion. Perhaps this whole issue will become moot once cheap hand-held methanol detectors become available.

[kennstminet]

there is an overwhelmingly popular myth among many home distillers

Never mind. This methanol myth has been busted here at HD and at many other places years ago.
The EU study is almost 30 years old and the knowledge about methanol behavior has grown since that time. There are many other scinentific reports from other sources with similar results.
If you search here at the forum, you will find multiple topics explaining those facts and busting the myth.
You are not alone with this misconception. And now, you know better.

[mark_m]

Fair enough. Have you thought about penning a "Novice's Guide to Understanding Methanol" to put in the appropriate place in HD?