Petroleum Ether Extraction

[junior_surgeon]

I have been attempting to create my own concretes/absolutes, and so far I have performed solvent (butane) extractions in an open loop system that allows the butane to escape. This produced mixed results and I'd like to refine the method further.

I recently saw mention of a commercial production method for absolute creation that involved the use of petroleum ether as a solvent, and am curious if anyone had experience with it? As far as I can tell, these petroleum ether extractions are performed using a Soxhlet apparatus and I'm also curious if anyone here has used such equipment.

And bonus question, is there any benefit in using petroleum ether over hexane aside from the safety hazard that hexane presents?

[xii]

I have been attempting to create my own concretes/absolutes, and so far I have performed solvent (butane) extractions in an open loop system that allows the butane to escape. This produced mixed results and I'd like to refine the method further.

I recently saw mention of a commercial production method for absolute creation that involved the use of petroleum ether as a solvent, and am curious if anyone had experience with it? As far as I can tell, these petroleum ether extractions are performed using a Soxhlet apparatus and I'm also curious if anyone here has used such equipment.

And bonus question, is there any benefit in using petroleum ether over hexane aside from the safety hazard that hexane presents?

I used petrol ether in soxhlet quite a bit. It works just fine. There are some problems though. The fractions that go into the adaptor are lighter and may start to boil receiving the heat from the flask through the bottom of the adaptor. This can be easily remedied by distilling lighter fractions first (in soxhlet with outlet blocked if lazy) and using them in the apparatus. I've got some rather spectacular concretes from tobacco and oakmoss (self collected) but it can become quite tedious. I spent two weeks extracting roughly 1,5 kg of untreated tobacco while the apparatus was in continuous use, recharged every 6-8 hours.
I'd use pentane instead of hexane unless under a fume hood. To my initial surprise, the physical properties of pentane extracts tend to differ from ones made with hexane but it shouldn't matter in perfumes.

[Bill Roberts]

From extractions for nutraceutical purposes and just chemistry in general, and you may already know as nothing in the above suggests not:

Petroleum ether is simply a light hydrocarbons mixture meeting given specifications and isn't a particular compound, nor an ether in the functional group sense.

I used it quite a bit as a graduate student simply from it being there and having uses, but afterwards I never found anything for which it was more suited (other than perhaps cost) than pentane, n-hexane, or mixed hexanes and it can be less suited.

[junior_surgeon]

I used petrol ether in soxhlet quite a bit. It works just fine. There are some problems though. The fractions that go into the adaptor are lighter and may start to boil receiving the heat from the flask through the bottom of the adaptor. This can be easily remedied by distilling lighter fractions first (in soxhlet with outlet blocked if lazy) and using them in the apparatus. I've got some rather spectacular concretes from tobacco and oakmoss (self collected) but it can become quite tedious. I spent two weeks extracting roughly 1,5 kg of untreated tobacco while the apparatus was in continuous use, recharged every 6-8 hours.
I'd use pentane instead of hexane unless under a fume hood. To my initial surprise, the physical properties of pentane extracts tend to differ from ones made with hexane but it shouldn't matter in perfumes.

Thank you so much for your input! A few questions though, when say "recharge" are you meaning the addition of more solvent? What kind of yields are you getting from materials like tobacco or oakmoss? And what are you using for a heat source?

[xii]

Thank you so much for your input! A few questions though, when say "recharge" are you meaning the addition of more solvent? What kind of yields are you getting from materials like tobacco or oakmoss? And what are you using for a heat source?

I use a heating mantle, which seems safe enough. I actually managed once not to turn the water in the condenser on and the petrol ether was spluttering all over without catching fire. By recharging I mean replacing the used material. Only 30g of tobacco could be fit in my 150 ml adaptor. I also needed to replenish the solvent lost with the used material being removed.

The yield from tobacco is a bit tricky. Initially 1% - 2% but a lot of that was water soluble, sugars and salts I presume, and interfered with nicotine separation. So I had to wash it first with water losing about half then with weak acid for nicotine removal which made it even less. If I remember correctly I got only 2g of absolute having washed the concrete with ethanol. I bought 1kg of low nicotine Virginian tobacco but the seller was generous and it was closer to 1,5 kg. Now that I have some experience with it I'd probably get about 5g. I got a very good yield from a small test run with Burley and the nicotine removal was very easy. Which can be tested with TLC, by the way. However, my Burley extract is quite similar to commercial tobacco absolutes even those from Virginian tobacco, whereas my Virginian tobacco extract is a different beast altogether. I'd estimate the absolute nicotine free yield from Burley to be around 0,5%.

I got about 0,5% yield from oakmoss, if I remember correctly, but it was a learning run so I guess I could beat it too.

Of course it's much cheaper to just buy these absolutes.

[mnitabach]

Of course it's much cheaper to just buy these absolutes.

But then you miss out on the excitement of potentially blowing up your house! ;-)

[xii]

But then you miss out on the excitement of potentially blowing up your house! ;-)

That's only one of the perks. Instant depilation while disposing the used material in a fire bowl is another.

[junior_surgeon]

I use a heating mantle, which seems safe enough. I actually managed once not to turn the water in the condenser on and the petrol ether was spluttering all over without catching fire. By recharging I mean replacing the used material. Only 30g of tobacco could be fit in my 150 ml adaptor. I also needed to replenish the solvent lost with the used material being removed.

The yield from tobacco is a bit tricky. Initially 1% - 2% but a lot of that was water soluble, sugars and salts I presume, and interfered with nicotine separation. So I had to wash it first with water losing about half then with weak acid for nicotine removal which made it even less. If I remember correctly I got only 2g of absolute having washed the concrete with ethanol. I bought 1kg of low nicotine Virginian tobacco but the seller was generous and it was closer to 1,5 kg. Now that I have some experience with it I'd probably get about 5g. I got a very good yield from a small test run with Burley and the nicotine removal was very easy. Which can be tested with TLC, by the way. However, my Burley extract is quite similar to commercial tobacco absolutes even those from Virginian tobacco, whereas my Virginian tobacco extract is a different beast altogether. I'd estimate the absolute nicotine free yield from Burley to be around 0,5%.

I got about 0,5% yield from oakmoss, if I remember correctly, but it was a learning run so I guess I could beat it too.

Of course it's much cheaper to just buy these absolutes.

Thanks again for the responses, low yield but about what I was thinking. I doubt I could make any higher quality extractions than commercially available products, but I'm mostly looking to extract materials that aren't already available to purchase.

[xii]

I'd expect rather good results from extracting spices. I did these too in soxhlet but with ethanol which picks way more colour than petrol ether.

[junior_surgeon]

Finally ordered a 1000ml Soxhlet chamber setup and a couple gallons of petroleum ether. I'll update with results when it gets here (and after I work out the inevitable kinks).

[refael_sakura]

Thanks for the post. I do have a soxhlet extractor. Used it once but with rosemary but didn't have such good results. Used it with water though . , woukd you make a tutorial video?


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[junior_surgeon]

Thanks for the post. I do have a soxhlet extractor. Used it once but with rosemary but didn't have such good results. Used it with water though . , woukd you make a tutorial video?


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Not much of a video guy, but possibly. There are some decent videos out there already of soxhlet extractions too, this is one of the ones I watched:

https://www.youtube.com/watch?v=mLq3...nel=mpnorganic

[junior_surgeon]

Got the extraction equipment today and a gallon of petroleum ether, I'm still waiting on the tubing but once that arrives I'll test it out and update with results.

Here is the soxhlet (it has since been moved from this precarious position):

Attachment 148440

[mnitabach]

Please don't blow yr house up!

[junior_surgeon]

Please don't blow yr house up!

I'll do my best not to!

[Bill Roberts]

Obviously I'm uselessly or near-uselessly late with this, but...

Petroleum ether is a rather variable product. Some products have a relatively high boiling point range due to mostly hexane/heptane composition, others low due to having pentane.

Websearching now for examples, one example is that Sigma-Aldrich offers it at 60-80 C bp range.

Your product is apparently 35-60 C, if I read the brand correctly and if their website is correct.

I'm expecting a fair amount of the lower boiling parts, namely the pentane component, is not going to re-condense but will go into your air. Use good ventilation.

[junior_surgeon]

Obviously I'm uselessly or near-uselessly late with this, but...

Petroleum ether is a rather variable product. Some products have a relatively high boiling point range due to mostly hexane/heptane composition, others low due to having pentane.

Websearching now for examples, one example is that Sigma-Aldrich offers it at 60-80 C bp range.

Your product is apparently 35-60 C, if I read the brand correctly and if their website is correct.

I'm expecting a fair amount of the lower boiling parts, namely the pentane component, is not going to re-condense but will go into your air. Use good ventilation.

Thanks for the input Bill, it's appreciated. I have an extra tube on the way that will fit over the top exhaust port and connect into the window ventilation board that I made for the laser engraver exhaust hose in the picture.

[xii]

Thanks for the input Bill, it's appreciated. I have an extra tube on the way that will fit over the top exhaust port and connect into the window ventilation board that I made for the laser engraver exhaust hose in the picture.

Ventilation is in any case a great advice.
The idea with the extra pipe leading outdoors is fine provided the outlet isn't much lower than the top of the condenser. Preferably higher.
Light hydrocarbons gladly turn into gas but absorb lots of energy in the proces. Once in the condenser, some heat gone, they return to the liquid form readily and rapidly. But you'll have to boil on very low heat or else the solvent will be pushed up the coils of the Graham condenser. The reason I use Allihn, which appears to suffice for pentane, by the way. I'm cooling with water at 10 degrees Celsius.

In general it's going to be a smooth process. Rather easy too. In case of any problems, the adaptor can behave weird, PM me.

[junior_surgeon]

Tested out the soxhlet setup yesterday using cranberry in the inaugural run with 200 proof alcohol as the solvent. The results were excellent! I loaded in about 18oz of chopped dried cranberries and ran it for about 2 hours, the yield was somewhere around *3.5z of a thick and fragrant cranberry extract. I had the heat a little high and the bottom started to burn at the end of the run, so that's something to watch out for in the future.

There were some kinks setting it up, but overall I am very impressed with the results and am excited to test this out with other samples and solvents.

Attachment 148724

[refael_sakura]

Cool stuff . I think I'll try that too . So sda40? As solvent? Why not a mixture with water? How cold do you keep the condenser? Isn't it better to keep it as colder as possible?( like ice water?

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[junior_surgeon]

Cool stuff . I think I'll try that too . So sda40? As solvent? Why not a mixture with water? How cold do you keep the condenser? Isn't it better to keep it as colder as possible?( like ice water?

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For this extraction I used perfumer's alcohol (200 proof) as the solvent, I don't know of any advantage to be gained in mixing with water but I would love to learn more, and I also have a gallon of petroleum ether that I plan on using soon to compare results. I purchased a small aquarium pump to use in the setup where it sits in a bowl of ice water and pumps the cold water into the condenser, though more ice has to be added as the heated water comes back out of the condenser.

[xii]

Adding water is a very bad idea leading to an inhomogeneous extract very difficult to handle. It won't affect the extraction itself though, as adapter gets azeotrope anyway.

[junior_surgeon]

Adding water is a very bad idea leading to an inhomogeneous extract very difficult to handle. It won't affect the extraction itself though, as adapter gets azeotrope anyway.

Thank you, I've appreciated your advice in getting this set up. I used the aquarium pump per your advice and the most recent run of cranberry turned out beautifully, no charring whatsoever.

[junior_surgeon]

From extractions for nutraceutical purposes and just chemistry in general, and you may already know as nothing in the above suggests not:

Petroleum ether is simply a light hydrocarbons mixture meeting given specifications and isn't a particular compound, nor an ether in the functional group sense.

I used it quite a bit as a graduate student simply from it being there and having uses, but afterwards I never found anything for which it was more suited (other than perhaps cost) than pentane, n-hexane, or mixed hexanes and it can be less suited.

I missed this comment before, but thank you for the input Bill. We have some pet ether in the lab and I figured it was a cocktail of alkanes, thanks for the clarification.

[Bill Roberts]

You're very welcome! However, I guess that it wasn't too much of a clarification, as "cocktail of alkanes" is a fair description, if meaning C5-C7 for some products and C6 & C7 for others.

What it is not, is an ether (in the usual chemical sense) or mixture of ethers.

It is an ether in an archaic sense.

[refael_sakura]

Adding water is a very bad idea leading to an inhomogeneous extract very difficult to handle. It won't affect the extraction itself though, as adapter gets azeotrope anyway.

I understand. So the extracted oil will be very "fragile" because it will have also hydrophilic molecules?

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[xii]

So the extracted oil will be very "fragile" because it will have also hydrophilic molecules?

Actually the opposite, the water soluble substances might get lost. It's a bit technical but might help getting better extracts:

As seen in #13, the apparatus has three major parts: flask, adapter and condenser from bottom to top. Initially all the solvent rests in the flask. When heat applied the solvent boils, turns into liquid in the condenser, and infuses the material in the adapter. Adding water to the ethanol in the flask doesn't influence much the solvent composition in the adapter, which is going to be an azeotrope, give or take. Once the solvent in the adapter, together with whatever it extracted, reaches certain level in will be drained back to the flask, which marks the end of a cycle. Once the last cycle is done, the solvent and anything it extracted lands in the flask. The next step is to remove the solvent and keep the extract. Most of the alcohol will evaporate easily, especially under vacuum, but at some point the water left behind will start to separate from the extract if it is not completely water soluble. At that point evaporation will start to leech the extracted material at an alarming rate, so the best idea is to simply dump the water phase together with whatever is solved in it. This leads to the loss of water soluble fraction of the extract.

[refael_sakura]

Actually the opposite, the water soluble substances might get lost. It's a bit technical but might help getting better extracts:

As seen in #13, the apparatus has three major parts: flask, adapter and condenser from bottom to top. Initially all the solvent rests in the flask. When heat applied the solvent boils, turns into liquid in the condenser, and infuses the material in the adapter. Adding water to the ethanol in the flask doesn't influence much the solvent composition in the adapter, which is going to be an azeotrope, give or take. Once the solvent in the adapter, together with whatever it extracted, reaches certain level in will be drained back to the flask, which marks the end of a cycle. Once the last cycle is done, the solvent and anything it extracted lands in the flask. The next step is to remove the solvent and keep the extract. Most of the alcohol will evaporate easily, especially under vacuum, but at some point the water left behind will start to separate from the extract if it is not completely water soluble. At that point evaporation will start to leech the extracted material at an alarming rate, so the best idea is to simply dump the water phase together with whatever is solved in it. This leads to the loss of water soluble fraction of the extract.

Thanks the detailed explanation. Makes complete sence. Should have figured it out myself.
Just on the go ... so pretty much after evaporating you have left with ..let's say... e.o or abs or concrete? Depense which solvent you use? Hexene will leave a concrete matter after evaporating? Or let's say you get some extract. How would you go about to bring it into crystal form? Lets say, like the video (I have watched it as well) of extracting nutmeg. What would be next step to separate the chemicals to form crystals from the main ingredients? Just wondering.

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