Hey guys, just got a rotovap and was looking around and getting some conflicting info so i figured id ask. Can pentane be used in the rotovap? I tried the oilxgreen thing and it worked ok but didn’t recover much and was hoping the roto would do a better job. Any insight would be appreciated.
It’s about your vacuum pump
do you really need one with pentane?
@Lost710 what do you have for cooling, and vacuum on your rotovap?
you don’t want much heat, or much vac, you want plenty of cold, and ideally you’re using an aspirator style vac pump, or some other form of explosion proof pump.
Cold trap is critical if you’re doing something stupid like running any old vac pump.
you’ll also need a controlled leak to get your vac level right.
you can get away without a vac pump, depending on what your goals/next steps are (think “passive recovery” use cold as the driver, not heat).
Do you understand the Antoine equation?
see if you can find data for pentane and understand what vac depth is doing for this particular solvent.
check out Pentane - Thermophysical Properties for numbers to plug in.
I have a aspirator style vac and ty for that data
Yeah i understand that part
Your info is way better, it’s too late for my brain to be properly functional. I personally don’t mess with pentane
Pentane gets a bad rep imo…
I get high returns of nice gold sometimes light gold depending on how long i let it sit and how cold i keep everything. After purge and decarb there is no real residual leftovers. I also am looking at some of these other members using it for diamond mining.
You might want to learn about the basics of distillation. Pentane can be evaporated in a Rotavap just like any solvent, provided the conditions are right (pressure, condenser temperature etc.)
It’s about pentane exploding.
Better use a vacuum regulator, or at least a manual valve to increase the vacuum if necessary.
Hi @Lost710 ,
With the appropriate vacuum source easy peasy. The bp is low so I would suggest a nomograph to determine it’s bp under reduced atmosphere.
You will want to apply the 20/40/60 rule to it so you have the adjusted bath temp/ condenser temp.
Awesome stuff! Imma stay with etoh with this for now and keep this in mind. You guys are bosses lol
Pentane can easily be recovered in the rotovap but generally we ask before we spec the equipment because pentane recovery requires a lower cooling range. Generally with ethanol you can run a chiller with a 5 to 25°C range, but with petane you need a colder chiller. Something that goes down to -30°C or more. Otherwise you’ll need to add some cold traps to prevent pentane vapor from exiting the system.
Hey guys, pentane doesn’t need a hard vac. So gimme a break with this cold trap stuff.
All you need is to pull an initial vacuum to-15 hg and set a vacuum regulator at that pressure. Or you can manually regulate the pressure to stay at -15.
Evaporation temp set to 32 c and chilling coil set to 0c.
A hard vac will be dangerous and wasteful.
I like to recover pentane in my closed loop system. Pull a full vac on system and use a hose as a diptube to fill your evaporation pot with pentane. Heat the pot in hot water. Can be boiling hot for all I care lol. Pull a vac with a recovery pump, and push through a condensing coil submerged in cooling water bath. No need to overkill it. A 55 gal reservoir with a air cooled radiator can do the trick lol. Pentane should condense at 97 f so as long as your water is colder than that you will be fine.
Don’t have a recovery pump? Run it passive with ice water or dry ice/ alcohol
I was reading ur teks. Had my head spinning
Yes you are right. In fact is boils low enough that you don’t need any vacuum. A light vacuum of 15" Hg is plenty. In my experience most people will still use the pump to speed things up which is where the cold trap comes into play. Not to protect the pump but to protect the operator from overexposure. As long as you have a moderate air exchange then it is not needed and really the cold trap just catches that extra 1-5% that escapes every run.
Continuously pulling a vacuum will speed up evaporation for sure, but will likely also decrease the extent of recovery as most vapor will leave into the pump. I believe the limiting factor is in general the condensation capacity, i.e. the chiller temperature and cooler shape/area. One just need to pull a vac until the condensator is close to saturation. Then the system can be closed until condensation rate decreases too much.