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Katie
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[*] posted on 26-4-2020 at 22:18
Vacuum pump for vacuum distillation.


I’m looking for advice on a vacuum setup that will work for vacuum distillation, other than an expensive chemical resistant membrane filter!

I’d spend up to $500 for an actual purpose built vacuum distillation pump that would last, or up to around $150-200 for one that will get the job done and last for at least more than a few distillations, or up to $80 for one that will work for a single nitric acid distillation! I really just want to do a small WFNA nitroglycerin synth for the historical significance of it! I have 500ml of 70% nitric acid.

Anyone have suggestions?
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[*] posted on 27-4-2020 at 00:36


I think that for your purpose, the best and I think only way is to buy water jet vacuum pump along with some efficient aquarium filter pump. Both of these are quite cheap and the corrosive vapors of nitric oxide will dissolve in water.
If you have efficient aquarium pump, you can pull quite decent vacuum.
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[*] posted on 27-4-2020 at 05:41


I'm not aware that the azeotrope of Nitric acid and water changes substantially with pressure (but happy to be corrected if it is the case), so I'm not sure that distillation would be of any use to you in producing WFNA.
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[*] posted on 27-4-2020 at 06:22


Pretty sure H2SO4 will be used in conjunction during the distillation.
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[*] posted on 27-4-2020 at 09:00
Hydroaspirator


http://www.sciencemadness.org/talk/viewthread.php?tid=1649#p...

Katie, this is one of my older posts. If you scroll up you'll see a
picture of my vacuum apparatus and how I use it. The
The hydroaspirator was always my favorite for producing
WFNA.




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[*] posted on 27-4-2020 at 10:03


for vacuum distillation you don't need a Vacuum pump per se. "vacuum distillation" really means reduce pressure distillation.one time my Vacuum pump didn't work so i distilled some water by adding water and a stirbar to vacuum distillation apparatuses that can keep a vacuum for days without giving up.first with no water at the cooling condenser(empty) i cranked the heat full so entire setup will fill with steam and so would escape from the "vacuum outlet". i attached one way valve so only steam can get out then cut off heat and let the water cooled till about 40C. at this point one way valve has don it's job and no air is inside only water vapor. turned on stirring (necessary for reduce pressure distillation ) and the cooling water and slowly up the heat till thermometer showed that water is distilling at 40-50C.

the moral of the story is that you don't need to keep the vacuum pumped running or connected one you created a vacuum in the first place and long a you don't lose it.
i distilled Glycerol by first heating it up to 110C to remove water and after it cooled down and adding it to a vacuum distillation apparatuses and pulling a vacuum and closing the valve that between pump and the setup. and heating cooling and most importantly stirring.




acid that repeat its qualities called "Periodic acid".
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[*] posted on 27-4-2020 at 13:00


Aspirators are dirt cheap.

I wouldn't bother with the pump if you're not using it often.

Just put it on a hose, or threaded faucet.

If you're panicked about wasting water save it in a garbage can and water the yard later.




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[*] posted on 27-4-2020 at 14:28


Quote: Originally posted by RedDwarf  
I'm not aware that the azeotrope of Nitric acid and water changes substantially with pressure (but happy to be corrected if it is the case), so I'm not sure that distillation would be of any use to you in producing WFNA.


No, but the lower boiling temperature means you get less decomposition to nitrogen oxides.




As below, so above.
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[*] posted on 27-4-2020 at 17:01


You can buy a half decent mechanical vacuum pump from an HVAC supply place for a few hundred bucks. Or you can look on here and find threads on making a pump from an old refriderator. That would work, but other than that, trying to find anything better than an aspirator for a good price can be tough. And the fumes from distilling strong acids will trash most pumps quickly if you don't have a good acid trap, which is not trivial. If you use a few moisture traps and backflow traps, an aspriator might be OK, but will not pull a strong vacuum. But too much vacuum will remove some of the nitric oxides, I think.
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[*] posted on 28-4-2020 at 18:22


Quote: Originally posted by rockyit98  
for vacuum distillation you don't need a Vacuum pump per se. "vacuum distillation" really means reduce pressure distillation.one time my Vacuum pump didn't work so i distilled some water by adding water and a stirbar to vacuum distillation apparatuses that can keep a vacuum for days without giving up.first with no water at the cooling condenser(empty) i cranked the heat full so entire setup will fill with steam and so would escape from the "vacuum outlet". i attached one way valve so only steam can get out then cut off heat and let the water cooled till about 40C. at this point one way valve has don it's job and no air is inside only water vapor. turned on stirring (necessary for reduce pressure distillation ) and the cooling water and slowly up the heat till thermometer showed that water is distilling at 40-50C.

the moral of the story is that you don't need to keep the vacuum pumped running or connected one you created a vacuum in the first place and long a you don't lose it.
i distilled Glycerol by first heating it up to 110C to remove water and after it cooled down and adding it to a vacuum distillation apparatuses and pulling a vacuum and closing the valve that between pump and the setup. and heating cooling and most importantly stirring.

This is very cool! So at what temperature did your Glycerol finally distill over at?
May I ask what was the size/scale/ground glass standard of your setup was?
Did you have any sort of vacuum gauge in line?

I finally acquired a cheap but pretty-damn-close to functional digital manometer, intended for HVAC use, along with one of their nicer pumps. I have thus far, set up my system :no matter how simple, tightly clamped, greased excessively, minimally, not at all - as soon as the vacuum pump turns off, (with the rest of the system ultra tightly sealed with gas rated close-off valve) the pressure starts rising. Sometimes super fast, sometimes it takes a few minutes to rise back up to atmospheric. I can't fathom how I could get it air tight enough to maintain and hold a low vacuum, especially to later perform a distillation!

I used Propylene Glycol as a standard and determined that my 7CFM fancy HVAC pump distilled PG at a temp that indicated I was at 2mmHG aka 2 torr aka 2000 microns, and my electronic micron gauge was reading it as 900 microns.
I paid $170 USD for the pump, including the digital micron gauge, and several different fittings. This was from a local classified ad.

Note: My A/C Condenser -> repurposed as vacuum pump pulls close to as much vacuum as the HVAC grade pump, without almost no sound, where as HVAC pump sounds like a robot alien invasion is coming.

Anyone have experience connecting such things in series? Or setting up a 2 step series? Yes the topic is covered in 10000 threads, but I never found nitty gritty details on connecting pumps in series.
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[*] posted on 29-4-2020 at 03:58


Quote: Originally posted by earpain  
Quote: Originally posted by rockyit98  
for vacuum distillation you don't need a Vacuum pump per se. "vacuum distillation" really means reduce pressure distillation.one time my Vacuum pump didn't work so i distilled some water by adding water and a stirbar to vacuum distillation apparatuses that can keep a vacuum for days without giving up.first with no water at the cooling condenser(empty) i cranked the heat full so entire setup will fill with steam and so would escape from the "vacuum outlet". i attached one way valve so only steam can get out then cut off heat and let the water cooled till about 40C. at this point one way valve has don it's job and no air is inside only water vapor. turned on stirring (necessary for reduce pressure distillation ) and the cooling water and slowly up the heat till thermometer showed that water is distilling at 40-50C.

the moral of the story is that you don't need to keep the vacuum pumped running or connected one you created a vacuum in the first place and long a you don't lose it.
i distilled Glycerol by first heating it up to 110C to remove water and after it cooled down and adding it to a vacuum distillation apparatuses and pulling a vacuum and closing the valve that between pump and the setup. and heating cooling and most importantly stirring.

This is very cool! So at what temperature did your Glycerol finally distill over at?
May I ask what was the size/scale/ground glass standard of your setup was?
Did you have any sort of vacuum gauge in line?

I finally acquired a cheap but pretty-damn-close to functional digital manometer, intended for HVAC use, along with one of their nicer pumps. I have thus far, set up my system :no matter how simple, tightly clamped, greased excessively, minimally, not at all - as soon as the vacuum pump turns off, (with the rest of the system ultra tightly sealed with gas rated close-off valve) the pressure starts rising. Sometimes super fast, sometimes it takes a few minutes to rise back up to atmospheric. I can't fathom how I could get it air tight enough to maintain and hold a low vacuum, especially to later perform a distillation!

I used Propylene Glycol as a standard and determined that my 7CFM fancy HVAC pump distilled PG at a temp that indicated I was at 2mmHG aka 2 torr aka 2000 microns, and my electronic micron gauge was reading it as 900 microns.
I paid $170 USD for the pump, including the digital micron gauge, and several different fittings. This was from a local classified ad.

Note: My A/C Condenser -> repurposed as vacuum pump pulls close to as much vacuum as the HVAC grade pump, without almost no sound, where as HVAC pump sounds like a robot alien invasion is coming.

Anyone have experience connecting such things in series? Or setting up a 2 step series? Yes the topic is covered in 10000 threads, but I never found nitty gritty details on connecting pumps in series.


It might be air leaking through your pump. Try adding a clamp between the pump and the vacuum take off adapter of your distillation apparatus. Something like https://www.thomassci.com/scientific-supplies/Screw-Compress... or something like https://www.amazon.com/Vise-Grip-RR-7-Inch-Locking-Pinch-Off...
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[*] posted on 29-4-2020 at 06:32


Quote: Originally posted by monolithic  
Quote: Originally posted by earpain  
Quote: Originally posted by rockyit98  
for vacuum distillation you don't need a Vacuum pump per se. "vacuum distillation" really means reduce pressure distillation.one time my Vacuum pump didn't work so i distilled some water by adding water and a stirbar to vacuum distillation apparatuses that can keep a vacuum for days without giving up.first with no water at the cooling condenser(empty) i cranked the heat full so entire setup will fill with steam and so would escape from the "vacuum outlet". i attached one way valve so only steam can get out then cut off heat and let the water cooled till about 40C. at this point one way valve has don it's job and no air is inside only water vapor. turned on stirring (necessary for reduce pressure distillation ) and the cooling water and slowly up the heat till thermometer showed that water is distilling at 40-50C.

the moral of the story is that you don't need to keep the vacuum pumped running or connected one you created a vacuum in the first place and long a you don't lose it.
i distilled Glycerol by first heating it up to 110C to remove water and after it cooled down and adding it to a vacuum distillation apparatuses and pulling a vacuum and closing the valve that between pump and the setup. and heating cooling and most importantly stirring.

This is very cool! So at what temperature did your Glycerol finally distill over at?
May I ask what was the size/scale/ground glass standard of your setup was?
Did you have any sort of vacuum gauge in line?

I finally acquired a cheap but pretty-damn-close to functional digital manometer, intended for HVAC use, along with one of their nicer pumps. I have thus far, set up my system :no matter how simple, tightly clamped, greased excessively, minimally, not at all - as soon as the vacuum pump turns off, (with the rest of the system ultra tightly sealed with gas rated close-off valve) the pressure starts rising. Sometimes super fast, sometimes it takes a few minutes to rise back up to atmospheric. I can't fathom how I could get it air tight enough to maintain and hold a low vacuum, especially to later perform a distillation!

I used Propylene Glycol as a standard and determined that my 7CFM fancy HVAC pump distilled PG at a temp that indicated I was at 2mmHG aka 2 torr aka 2000 microns, and my electronic micron gauge was reading it as 900 microns.
I paid $170 USD for the pump, including the digital micron gauge, and several different fittings. This was from a local classified ad.

Note: My A/C Condenser -> repurposed as vacuum pump pulls close to as much vacuum as the HVAC grade pump, without almost no sound, where as HVAC pump sounds like a robot alien invasion is coming.

Anyone have experience connecting such things in series? Or setting up a 2 step series? Yes the topic is covered in 10000 threads, but I never found nitty gritty details on connecting pumps in series.


It might be air leaking through your pump. Try adding a clamp between the pump and the vacuum take off adapter of your distillation apparatus. Something like https://www.thomassci.com/scientific-supplies/Screw-Compress... or something like https://www.amazon.com/Vise-Grip-RR-7-Inch-Locking-Pinch-Off...


Thank you, i never used one of those specifically, but the vacuum pump
has a built in heavy duty isolation valve between the pump itself and the outlet, which has a 3 way HVAC grade threaded fitting adapter. I have one sealed, one has the micron gauge connected, and the third goes to my distillation system, with a needle valve as the first object in line. I have verified deep vacuum when closing the needle valve from all of the glassware, and especially when also closing the lever to the pump itself. I do use flexible hosing with plastic nipples, there's probably no way around this issue without making everything from copper or aluminum tubing.
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[*] posted on 29-4-2020 at 10:06


I have successfully distilled multiple substances with aspirator vacuum.

But I also have refrigerator vacuuming pump that states it would reach 5Pa pressure.

Apparently vacuum of this scale reduces boiling points of most ordinary stuff so much it would become impossible to condense them.

Haven't tried to distill anything higher BP stuff with it, though. Haven been around my lab for a while, but now I'm tempted to test out to distill something with high, +250C bp, which should come over at around 45C. Distilling heavy molecules with gently heated water bath sounds very comfy now that I think of it.

[Edited on 29-4-2020 by Refinery]
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[*] posted on 29-4-2020 at 13:49


Everybody has said it already: get an aspirator. Easy to clean, cheap, definitely sufficient for nitric acid.

To make things more practical, I hooked my aspirator to a female quick disconnect fitting. The male quick-disconnect is on the faucet so I can setup and remove the aspirator in literally 2 seconds. Really handy.
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[*] posted on 30-4-2020 at 18:48


Quote: Originally posted by Refinery  
I have successfully distilled multiple substances with aspirator vacuum.

But I also have refrigerator vacuuming pump that states it would reach 5Pa pressure.

Apparently vacuum of this scale reduces boiling points of most ordinary stuff so much it would become impossible to condense them.

Haven't tried to distill anything higher BP stuff with it, though. Haven been around my lab for a while, but now I'm tempted to test out to distill something with high, +250C bp, which should come over at around 45C. Distilling heavy molecules with gently heated water bath sounds very comfy now that I think of it.


Inspired by Nerdrage's demo of his aspirator , and how he measured it , a bit elusively , but drove the abstraction deep into my brain and fully grasp that any pure liquid wit higher BP's will be more accurate than all of the manometers on earth.



Until you hit Molecular Vacuum of course

[Edited on 29-4-2020 by Refinery]
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[*] posted on 30-4-2020 at 19:24


I have used this one to reduce boiling points of esters with high boiling points, such as nonyl acetate. https://www.amazon.com/gp/product/B012CFTYX4/ref=ppx_yo_dt_b...





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[*] posted on 1-5-2020 at 06:58


Quote: Originally posted by Cou  
I have used this one to reduce boiling points of esters with high boiling points, such as nonyl acetate. https://www.amazon.com/gp/product/B012CFTYX4/ref=ppx_yo_dt_b...



I'm interested in buying one at the moment, as my rocker diaphragm pump turned out to have to weak vacuum for me (oscillating around 60mmhg it's good for distilling liquids with boiling point around 200 - 250C but as my lab skills evolve I need something better). When I purchased it I just had tuition from EU and had to buy some pump quickly and I had quite narrow knowledge about vacuum pumps, so I didn't know the difference in vacuum between oil and vacuum pumps. And oil pumps interested me with being very cheap actually, of course if you don't invest in some "good company" ones...

So can You tell me Cou, how the aparature handles such a low vacuum as 0.03 mmhg and do you use regular distillation apararture, or some with thicker glass?

Also can you regulate the vacuum pressure in the pump? Maybe you installed some valve for it, and is it even useful to regulate pressure on oil pump, or just use it all the time at "ultimate" level?

And one more thing, how is with the pump's failurity, are problems with it common or does it require special attention, with oil changing and stuff?



[Edited on 1-5-2020 by mackolol]
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[*] posted on 2-5-2020 at 20:39


Quote: Originally posted by mackolol  
Quote: Originally posted by Cou  
I have used this one to reduce boiling points of esters with high boiling points, such as nonyl acetate. https://www.amazon.com/gp/product/B012CFTYX4/ref=ppx_yo_dt_b...



I'm interested in buying one at the moment, as my rocker diaphragm pump turned out to have to weak vacuum for me (oscillating around 60mmhg it's good for distilling liquids with boiling point around 200 - 250C but as my lab skills evolve I need something better). When I purchased it I just had tuition from EU and had to buy some pump quickly and I had quite narrow knowledge about vacuum pumps, so I didn't know the difference in vacuum between oil and vacuum pumps. And oil pumps interested me with being very cheap actually, of course if you don't invest in some "good company" ones...

So can You tell me Cou, how the aparature handles such a low vacuum as 0.03 mmhg and do you use regular distillation apararture, or some with thicker glass?

Also can you regulate the vacuum pressure in the pump? Maybe you installed some valve for it, and is it even useful to regulate pressure on oil pump, or just use it all the time at "ultimate" level?

And one more thing, how is with the pump's failurity, are problems with it common or does it require special attention, with oil changing and stuff?



[Edited on 1-5-2020 by mackolol]


I used a T adapter to attach a vacuum gauge to the system. it only runs on full power, but you can maintain a vacuum of any level by turning it off quickly (only run for like 1 second) and partially releasing vacuum by slightly unscrewing release valve.

i don't have any experience with maintenance, failurity




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[*] posted on 2-5-2020 at 22:55


While connected to a vacuum some vacuum pumps will not start because of the limited starting torque from the motor.

In addition pumps containing oil can have the oil sucked into the compression chamber and then into the connected vacuum line. Because vacuum pumps are compression pumps they can not pump the almost compressible pump oil and will lock up tripping the breaker or the motor thermal cutout. The oil backing up into the vacuum line can happen very quickly (a few minutes) with old worn pumps.

The recommended method of connecting vacuum pump is via an inline valve with an air inlet valve connected between the inline valve and pump.




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[*] posted on 3-5-2020 at 02:28


And how does the glassware handle such a high vacuum at high temperatures?
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[*] posted on 3-5-2020 at 03:15


Quote: Originally posted by mackolol  
And how does the glassware handle such a high vacuum at high temperatures?


The difference in compressive force on the glassware between high vacuum or a perfect vacuum and 0.1 bar absolute is only 10% about the same as the changes in atmospheric pressure due to weather. Meaning it not significant.

For symmetrical tubes or spheres the glassware is under compression which makes it stronger. But most glassware is not perfectly symmetric and have defects so there are limitations. Ideally you would use glassware rated for vacuum as flat bottomed thick walled filter flasks are or consult the manufacture's spec for maximum temperature under vacuum.

In practice test the glass under vacuum and at the temperature it will be used at. You should also take precautions to reduce injury if it does fail.






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[*] posted on 3-5-2020 at 03:24


Ok. Since I have diaphragm pump I won't rather be using such high vacuum for filtrations.
I didn't really knew that it's not big difference to the glassware in these pressures (however 0.1 mmhg is 600 times bigger vacuum than 60mmhg which I usually obtained).
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[*] posted on 3-5-2020 at 16:39


Quote: Originally posted by mackolol  
Ok. Since I have diaphragm pump I won't rather be using such high vacuum for filtrations.
I didn't really knew that it's not big difference to the glassware in these pressures (however 0.1 mmhg is 600 times bigger vacuum than 60mmhg which I usually obtained).


Relative vs absolute. Most vacuum you can have is 760 mm Hg at sea level, and so 759.9 mm Hg vs 740.0 mm Hg is not that big of a difference. :)

As for controlling vacuum, needle valves work well although they aren't really for precision work. https://www.amazon.com/gp/product/B00FDWABLS/ref=ppx_yo_dt_b... Connect it to a "t" fitting with hose barbs on either end.

[Edited on 5-4-2020 by monolithic]

[Edited on 5-4-2020 by monolithic]
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[*] posted on 4-5-2020 at 01:41


As far as I know, they're usually installed to diaphragm pumps. Thanks for link.
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[*] posted on 4-5-2020 at 11:39


Quote: Originally posted by mackolol  


I'm interested in buying one at the moment, as my rocker diaphragm pump turned out to have to weak vacuum for me (oscillating around 60mmhg it's good for distilling liquids with boiling point around 200 - 250C but as my lab skills evolve I need something better). When I purchased it I just had tuition from EU and had to buy some pump quickly and I had quite narrow knowledge about vacuum pumps, so I didn't know the difference in vacuum between oil and vacuum pumps. And oil pumps interested me with being very cheap actually, of course if you don't invest in some "good company" ones...

So can You tell me Cou, how the aparature handles such a low vacuum as 0.03 mmhg and do you use regular distillation apararture, or some with thicker glass?

Also can you regulate the vacuum pressure in the pump? Maybe you installed some valve for it, and is it even useful to regulate pressure on oil pump, or just use it all the time at "ultimate" level?

And one more thing, how is with the pump's failurity, are problems with it common or does it require special attention, with oil changing and stuff?



[Edited on 1-5-2020 by mackolol]


Maybe my experience might be of help:
Before I had mentioned distilling Propylene Glycol , and using it's known BP at 1 ATM and its enthalpy of evaporation to determine that my entire distillation setup, flask-T/thermometer-leibig-flask-very thick tubing-bubbler as cold trap ->brass T with digital manometer->oil pump was able to -distill- at 2 mmHg. I now realize why the digital gauge was reading .9mmHg(it was right next to the vacuum source)

But I would like to say:
-removing off my glassware, my digital gauge has pulled down to .02 mmHg aka 20 microns. The pump is two stage and the specs say it should be able to pull down to .01.
-be it for distillations, or ESPECIALLY for filtrations, controlling the flow with a valve is essential. Does not have to be like a regulator , but a small needle valve, same one's used for torches is very important
-Anything that makes it past your trap, will go into the oil. This can be a good thing, not just a bad thing. One can simply close off the inlet, and let the pump run. the combination of vacuum and the oil heating up over time, will 'outgas', anything trapped in the oil. Which is usually H2O vapor. Or rather, it's H2O vapor that will limit the power of the vacuum pump.
-I just had an idea today. Will search to see if revious threads exist first
I have a small SPD head. My oil pump came with a small bottle of extra oil. THe manufacturer says 'change with every use' - lol. The HVAC guys don't fall for that anymore. I think i will attempt to distill my vacuum pump oil!!
SPD is designed for this and is used regularly in the petrol industry to distill the highest fractions of both crude oil and for recycling used motor oil.
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