Sciencemadness Discussion Board - Benzyl Alcohol from Green Stripper

Benzyl Alcohol from Green Stripper

JJay - 29-1-2017 at 20:01

Someone gave me a 3.75 L jug of biodegradable floor adhesive stripper that unfortunately doesn't contain any DCM. According to the MSDS, it contains some kind of clay, 5% surfactants, water, and 20-40% benzyl alcohol.

I'm not sure if the surfactants or the clay are interesting or useful things to have around, but I certainly wouldn't mind having some benzyl alcohol. I'm not 100% sure what I'm going to do with it, but it has numerous uses as both a solvent and as a building block, so it will be a welcome addition to my lab.

There seems to be very little information available on extracting benzyl alcohol from OTC products. It's very easy to buy as a reagent, but it's also used widely in consumer goods, so I am a bit surprised that no one has addressed this topic before.

I think I can steam distill out the benzyl alcohol pretty easily. It forms an azeotrope with water consisting of 9% benzyl alcohol at just under 100 C, and it will dissolve in water at 20 C at concentrations of about 4%. I think if I continually remove the organic layer and return the aqueous layer back to the boiling flask, I should end up with at least several hundred mL of benzyl alcohol, which I can then fractionate and store over [probably] molecular sieves.

I'd rather not lose a substantial portion of the recovery to the final aqueous layer, of course. Does anyone know how hard it is to salt out benzyl alcohol or what salts work best?

[Edited on 30-1-2017 by JJay]

DraconicAcid - 29-1-2017 at 20:57

If distillation doesn't work, I suspect that it would be easy to convert it to benzyl chloride with concentrated HCl, and that would be very easy to separate from the aqueous layer.

(I don't have a cite, but I remember a lab involving the structurally similar vallinyl alcohol, the extraction of which failed because the directions said to "cool in an ice bath, then neutralize with 6M hydrochloric acid", and the students assumed that since it didn't say anything about *keeping* the solution in the ice bath, the addition was done at room temperature.)

[Edited on 30-1-2017 by DraconicAcid]

JJay - 29-1-2017 at 22:00

Quote: Originally posted by DraconicAcid

If distillation doesn't work, I suspect that it would be easy to convert it to benzyl chloride with concentrated HCl, and that would be very easy to separate from the aqueous layer.

(I don't have a cite, but I remember a lab involving the structurally similar vallinyl alcohol, the extraction of which failed because the directions said to "cool in an ice bath, then neutralize with 6M hydrochloric acid", and the students assumed that since it didn't say anything about *keeping* the solution in the ice bath, the addition was done at room temperature.)

[Edited on 30-1-2017 by DraconicAcid]

Oh hahaha! That might be a little problematic to contain on this scale and would require ginormous amounts of HCl with all the water present. And I'm not sure what the surfactants would do. But hey, who doesn't need a visit from the friendly neighborhood firefighters' HAZMAT team from time to time.... I'm actually not sure what happens if you try to distill a 4% benzyl alcohol solution... freezing might work if distillation doesn't.

[Edited on 30-1-2017 by JJay]

DraconicAcid - 30-1-2017 at 09:41

Quote: Originally posted by JJay

Quote: Originally posted by DraconicAcid

I don't think it would have to be that concentrated, but it would depend on how basic those surfactants are...

Praxichys - 30-1-2017 at 11:24

You probably won't be able to steam distill because the surfactants will cause foaming.

There is probably a ton of surfactant in there to keep the benzyl alcohol in suspension since it's only like 3.5% soluble at room temp. You can try acidifying with a strong, nonvolitile mineral acid like sulfuric or phosphoric to break the surfactant. If that works, you might be able to distill it directly.

If it's still foamy after acidification, try basifying a portion and letting it sit at high temp for a while. There are many types of surfactants and some of them are tenacious as hell... I wish you luck.

JJay - 30-1-2017 at 11:33

The surfactants are ethoxylated C9-11 alcohols such as this one: http://www.chemicalland21.com/specialtychem/perchem/lauryl%2...

I'm pretty sure they have antifoam properties, but you may be right.

[Edited on 30-1-2017 by JJay]

DraconicAcid - 30-1-2017 at 11:41

If you don't want to try converting it to the chloride, I'd suggest salting it out. Sodium chloride might work if the solution is cold and not acidic. It if doesn't come out well, then add an organic solvent to extract it, washing it a couple of times. With any luck, the surfactants will stay in the aqueous layer, so that you can distill after that.

[Edited on 30-1-2017 by DraconicAcid]

JJay - 30-1-2017 at 11:48

I think sodium chloride might work too... I'm almost positive that potassium carbonate would work in sufficient concentration.

I'm pretty reluctant to make benzyl chloride out of it, especially for purification purposes. While I might want to make some at some point, it's not something I want sitting on the shelf.

LD5050 - 9-2-2017 at 21:07

Any update or success removing the benzyl alcohol?

JJay - 9-2-2017 at 21:12

I haven't gotten around to trying it yet, mainly because it is not a high priority project and will probably take all day, but I'm sure I'll get to it before the end of next weekend.

PHILOU Zrealone - 10-2-2017 at 12:22

Hey Benzyl chloride ---> STRONG LACRYMATOR

JJay - 10-2-2017 at 14:25

I'm picking up some 3 mL reaction vials today, so I'll consider it, but I've never handled any lachrymators before.

JJay - 12-2-2017 at 18:59

I'm still not really sure what I'm going to do with the benzyl alcohol, but I started steam distilling the stripper today. Right now, I'm watching milky drops form in my condenser and fall into a flask. The distillate smells faintly of almond flavoring, which I assume is due to oxidation. I will say this: Distilling benzyl alcohol from paint stripper is not for the faint of heart. As the mixture heats up, the surfactant separates out with severe bumping, which continues as the mixture distills. It seems harmless now, but the bumping was pretty scary earlier. If I ever do this again, I'll use stirring.

I'm not completely sure how much benzyl alcohol is in the distillate, but it is clear as it makes its way up my Vigreux and turns milky in my Graham condenser. I can see oily drops forming on top of the milky distillate... which seems odd since benzyl alcohol is heavier than water, so perhaps they are held there by surface tension.

I don't think a fractionating column is really necessary for stripping benzyl alcohol out of stripper, but without it, the bumping would surely be throwing a lot of gunk into the distillate.

[Edited on 13-2-2017 by JJay]

JJay - 12-2-2017 at 20:24

Everything is very easy and straightforward so far aside from the bumping. The oily drops floating on top eventually coalesce and fall to the bottom. Theoretically, there should be about 50 mL of benzyl alcohol per liter of distillate until the concentration in the boiling flask falls too low, at which point I guess salting out the benzyl alcohol might work.

LD5050 - 12-2-2017 at 21:30

Interesting.. Please keep updating. I use benzyl alcohol a lot and oxidize it into benzaldehyde using mangenese dioxide from batteries it works quite well the only down side is working with the mangenese, it makes a mess of everything.

JJay - 12-2-2017 at 22:54

Oh... I've never tried anything like that.

A particularly nasty bump blew apart the apparatus. Nothing broke, but I only have a little bit of product, and it need to be dried and fractionated. I did try hooking up my stirrer, but it only has one speed, which is something like "vanquish." It's certainly fast enough. It burned the o-ring out of my bearing and is really too unstable with the stands I have, so I'm going to put this on hold while I get some new stands....

Edit: Scratch that. It just occurred to me that I can swap in my new Dimroth condenser for the Graham condenser, and it should have less trouble with handling bumps without stirring while still being highly efficient.

[Edited on 13-2-2017 by JJay]

JJay - 13-2-2017 at 01:15

The Dimroth condenser seems to work well for condensing the erratic vapors from the green stripper. The bumping is really something to behold... at times, the mixture will be sitting there with nothing condensing for a full minute and then it will bump hard and go into a raging boil that fills the flask with foam for 30 seconds, running vapors halfway down the condenser. I did have a gas inlet adapter over one neck of the receiving flask but removed it and replaced it with an air condenser to keep pressure from building up with the bumps. It's definitely one of the more exciting distillations I've done.

JJay - 13-2-2017 at 03:54

It's still bumping along happily. I added a few more clamps to keep it from spraying boiling paint stripper around the room at the hardest bumps. Some benzyl alcohol oil is floating on top of the distillate, some is collected in a puddle on the bottom, some of it is dissolved, and some of it is just floating around in tiny droplets. I'm pretty sure I'm going to have to salt it out to achieve even a 5% recovery rate. This definitely seems to work, but it's pretty slow. I'm curious about how vacuum distillation might go... I suspect it would be a disaster with all the surfactant present, but who knows... it might actually be very easy.

Update: I took about 500 mL of the distillate (which was cloudy and had oil floating on top, in a puddle at the bottom, stuck to the sides, and floating around in tiny globules) and added 150 grams of impure sodium chloride that I had previously used in a salt bath and shook it until it dissolved. A small but significant organic layer formed on top of the solution. I shook the flask to disperse the oil layer and added everything to a separatory funnel and let it separate into layers and then drained the layers into different flasks. The organic layer, while certainly still impure, measured nearly 50 mL.

So it looks like salting out works and works pretty well. I'm holding onto the aqueous layer for now. My original plan was to simply use it to provide water for steam distillation, but it was hard to separate the oil without salting it, and I'm not 100% sure that adding salt to the boiling flask is a good idea... it am guessing that it might make the bumping even worse.

So anyway, I realize that this isn't exactly frankincense and myrrh that I'm working with here, but it does seem that steam distillation works pretty well for getting benzyl alcohol out of OTC stripper.

[Edited on 13-2-2017 by JJay]

Amos - 13-2-2017 at 10:51

What's the product name? Any idea where it can be purchased?

Praxichys - 13-2-2017 at 11:16

The Klean-Strip brand "green floor adhesive remover" at Home Depot has 30-40% benzyl alcohol. Not sure if it's the same stuff though.

JJay - 13-2-2017 at 15:52

It's Klean Strip. There are a lot of other strippers that contain benzyl alcohol too.

JJay - 14-2-2017 at 18:38

So anyway, I've been running this off and on over the past few days, and after distilling off about 1.5 L of water, the bumping all but stopped. I continued adding water periodically, trying to keep pace with the distillation. After about 2L of distillate had been taken off, the mixture began bumping extremely violently, to the point where it was actually throwing surfactant through my 30 cm Vigreaux. A little bit got into the distillate but was pretty easy to separate, although getting the surfactant out of the sep funnel required taking it apart.

I think the water that I was adding was having trouble penetrating the blobs of surfactant and for that reason, there were some localized blobs of surfactant that contained mostly benzyl alcohol with little water. These occasionally found their way to the side of the flask, where I think they were superheated by the mantle and exploded like little aromatic hot dogs but with the violence of something more like a large kielbasa.

At this point, I have a little less than 200 mL of benzyl alcohol, which still needs to be purified. I figure I'll dilute the stripper back to its original volume and thoroughly homogenize it and then see if I can get some more benzyl alcohol out of it before vacuum fractionation (or alternatively, I might locate an extremely sturdy stand for my stirrer). This is a pretty good stopping point for the time being; I took the apparatus apart and cleaned most of the glass, although the worst parts are soaking in a 20L bucket. Removing the addition funnel from the flask required soaking both for a few minutes, but after that, the funnel came out pretty easily.

[Edited on 15-2-2017 by JJay]

JJay - 16-2-2017 at 02:08

Ok, this will probably be my last update on this thread, but I ended up diluting the stripper about 50/50 with water and decided to take my own advice and use a pressure cooker pot still for the distillation. I'm using a large pressure cooker (maybe 15L) with a 1000 watt hotplate, with a simple 1/4 inch copper tube through the lid hooked to a condenser with a thermometer adapter. I sealed everything up using flour paste. This is an extremely easy and pleasant distillation, and it's going fast. I can see a lot of oil in the distillate.

JJay - 16-2-2017 at 22:59

Well, as it turns out, the stripper acted on the pressure cooker gasket, swelling it. So now I will need a new gasket unless I can shrink the one I have. I threw out the rest of the stripper after recovering about 450 mL of crude product. There was more to recover, but I got tired of fooling with it. I figured, though, that I should make a picture post.

[Edited on 17-2-2017 by JJay]