Question regarding ethanol recovery and if I’m doing things right. It seems over time I’m losing quite a bit of ethanol. My empty everclear bottles are stacking up. Here’s my process after making bho/crude
I dilute 2 oz crude with 20oz everclear. I mix them together on a hot plate to dilute, usually around 95f-100f gets me a nice mix. Is that temp ok? I assume I’m starting to lose the everclear here due to evaporation.
Then I take that mix In a jar and freeze it… dry ice if I have, otherwise deep freezer for a day or two. Filter through 3 micron paper in Buchner. This is where I Assume I lost more ethanol, in what gets binded with fats etc and doesn’t make It through the funnel. I run the Buchner until I can it as dry as I can by spreading the material around to keep a seal and pull as much through.
After the Buchner I put it into my rotovap. 5L best value vacs rotovap. I run it at 100F, at 100 rpms. My chiller has trouble keeping it steady chilled once I start running it. But I noticed eventually as the oil thickens up and ethanol is removed , my chiller will start going back down. It will start at -20c, make it up to roughly 20c, and eventually start going back down. I run the rotovap until the drops slow to near stop/no drops or until the oil gets real thick and starts coating the walls of the flask.
And that’s my method. So, how much everclear should I be losing? We keep careful track of what goes in and what comes out, of both oil and everclear. For instance recently I ran a jar of a few batches that had approx 40 oz everclear, and I got back approx 32.30 oz. almost 8 oz gone?
So with all that rambling, where am I going wrong, or are my numbers expected for the process I put it through. I never feel like I get all the ethanol out of the oil, but don’t want to over do it in the rotovap
I figured a lot had to be going right into my pump in the market for a nice big cold trap for both this and my short path setup I’m putting together. Thanks for that tidbit
We are looking to upgrade the chiller for sure, but also plan on soon purchasing a nice heavy duty cold trap. But I’m glad I got a pretty solid response from two people about the vapor being lost during rotovap. Today I was like damn, where did all these empty everclear bottles come from lol
You don’t need a big fancy cold trap. Something simple will work. I have one from Open-Source Steel that works pretty well for my low-vacuum applications. I use it on my 50L rotovap and it works well.
Your SOPs are solid and your solvent loss is about normal. We recently switched to etoh denatured with heptane to save $.
Also, instead of investing in a larger chiller, you can drop dry ice into your chiller’s reservoir to keep the temps down. Try and stay below 10f.
What kind of pump are you using? Rotary vane or diaphragm/scroll?
currenty im using the bestvaluevacs 2 stage pump, nothing crazy but i did just get a welch duoseal 1400 in the mail yesterday so i hope to be using that soon with the roto and my distillation. The reason for the more “fancy” cold trap would be to have it in the future when we start upscaling. We are still small time, and even when we upscale we wont be industry huge, but i have the capital available to make some smarter long term purchases so i figured a nice cold trap would be used a lot. you guys rock for sure… im pretty sure as said by a few people, im losing most my etho in the roto vap due to not being chilled enough
We have a smaller dedicated pump for the rotovap. It was just an idea since we have the welch, but agree it doesn’t need to be running if not necessary
can anyone suggest a good cold trap for purchase? As of now, we will be using it for both our rotovap, as well as or distillation setup which is fairly small for now. Ive checked bestvaluevacs and open source steel thus far… they all seem to be very different, just wondering what my best choice would be for my applications. Unless im running the CLS, dry ice is usually not on hand and available an hour away, so using dry ice is somewhat a pain, but i also assume my next choice is an electric cold trap which can run a few grand. its not out of the question, as we plan to upscale down the line, but i just need help choosing a cold trap and what makes some better than others
What percentage of ethanol loss from dying reclaimed EtOH with 3A molecular sieves are you guys seeing??
I tried it a couple of times, at two to one EtOH to sieves I lost nearly 50% of the EtOH, and at three to one about a third. Way to high a loss for my liking.
Can I place the wet sieves in my distiller and pull off the EtOH???
I’m distilling 40% vodka to 95%+++ The highest percentage I can get with my water distiller is about 92%, after that the increases are extremely incremental, therefore the 3A molecular sieves. I get it that a reflux still would get me to the azeotrope in a single pass.
I added a high percentage of sieves to some 92.25% by volume and it went to 99.0%, but I lost nearly 50% of what I started with.
I then added a lower percentage of sieves to some 92.0% and it went to 96.0%, but I lost about a third of what I started with.
I have the 96% soaking with a high percentage of sieves right now, later today I’m going to filter, and then place the sieves in my water distiller with the wattage to the heater dialed way down, probably less than a hundred watts, and use the temperature controller to keep the vessel base temperature at just under the boiling point of water.
To state the perceived problem again, I’m seeing a huge amount of ethanol loss to remove a small amount of water.
Is the ethanol I’m losing held within the beads, on the surface of the beads, or what??? Supposedly the 3A sieves can’t absorb ethanol, can they somehow absorb the azeotrope? Hopefully by this afternoon I’ll have some clues.
Btw, the temperature you take hydrometer readings at makes a significant difference in accuracy. I keep the graduated cylinder and hydrometer in the fridge along with what I’m going to test. I then place a probe in the cylinder and wait for the temperature to rise to 60F to take the reading.
I got this for my buchner set up and ended up using it on my lil 5 liter rotovap.
I wouldnt use your duoseal. That pump oil is expensive.
If you don’t have dry ice around, you can put a regular Ice Pack in there. Just keep swapping them in and out of the freezer. Just don’t use regular ice because it will dilute your coolant. I used to throw frozen chicken breasts in there in my black market lab jajajajaja
My first try at this worked, I need to discover the best process.
I added a pound of 3A molecular sieves to 915mL of 96.0% by volume EtOH which produced 715mL of 98.5% by volume EtOH, a loss of 200mL EtOH/H2O. I figure the 200mL to be about 175ml EtOH and 25mL H2O.
I then placed the sieves in my modified water distiller, and with the wattage limited to 75 watts I distilled letting the temperature rise slowly to 275F (measured with a thermocouple sensor attached to the outside center bottom of the vessel - this was the highest temperature I cared to take the distiller.) I tried controlling the temperature during distillation, but the drip rate was way too slow. When I opened the distiller the beads were no longer soaking wet, but still had a strong odor of EtOH. I got 67mL of about 99% by volume EtOH (I used a 10mL graduated cylinder and a centigram scale to measure the density since I didn’t have enough to use a hydrometer.)
I added enough distilled water to the distiller vessel to cover the sieves and distilled them again, this time I used 100 watts to Limit (full stop) at 215F. I got 49mL of about 65% EtOH.
About 100 mL of EtOH retrieved from 175mL of ‘lost’ EtOH. Considering the first 67mL was nearly pure EtOH, this would be a major save if drying out large amounts of sieves.
Do you rinse your zeolites with water afterwards? Just surface coating the lb of beads is going to have a noticeable loss in ethanol. Rinse them with water then redistill and you’ll likely be able to recover a bunch of that.
in the market for a nice big cold trap for both this and my short path setup I’m putting together. Thanks for that tidbit