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497
National Hazard
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Propylene (oxide) synthesis
What is a practical OTC source of propylene? There are many options that I see, few look usable though. In the end I want propylene oxide, but I have
everything else worked out except for a propylene source.
Isopropyl alcohol can be dehydrated to propylene. From what I have seen in patents it cannot be done as ethylene is synthesized from ethanol because
of polymerization cause by the sulfuric acid. Is this true? Could it be done without too much trouble, even if the yield is not great? I have found
few details. I have found details that say that a silica gel-alumina catalyst will very efficiently dehydrate alcohols including isopropyl.
Unfortunately it is the high temp, high pressure gas phase type reaction that would be a major pain in the ass to set up.
Dehydrogenation of propane comes to mind. I have found plenty of info on it, but its all industrial scale with exotic catalysts and high pressures...
maybe there's a way to do it small scale?
Pyrolyzing butane. The yield sucks and I have found few details, Butane is cheap, and as long as the separation from byproducts is not too hard, it
might be usable?
Possibly dehydration of propylene glycol? With certain catalysts it is said to give propylene oxide. Since propylene oxide is actually my end goal
that would be great. Unfortunately selectivity seems to be low and give mostly propionaldehyde and acetone. I need to look into it more.
I looked into pyrolyzing polypropylene, but alas it just gives a bunch of complex branched hydrocarbons and little if any propylene...
Any ideas or comments?
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not_important
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The vapour phase dehydration of isopropanol over Al2O3 does not require high pressure, and temperatures are in the 200 to 300 C range.
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497
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Hmm yes that may be the best option. Yeild will probably be worse with low pressure but that doesn't matter much considering the price of isopropyl. I
would still like to avoid vapor phase reactions if i can, but it may be my only option..
Also I wondering about butanol, would it work the same? I don't see why not.
[Edited on 2-8-2008 by 497]
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DJF90
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Heating (and refluxing) with conc. sulphuric or phosphoric acid is also standard procedure. Just remember the product is in the gas phase...
[Edited on 2-8-2008 by DJF90]
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Polverone
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You can convert hot propylene glycol to chlorohydrin with HCl gas then react the chlorohydrin with base to form propylene oxide. In some places
propylene gas is available in cylinders as a torch fuel. In some places propylene oxide itself is available as a go-kart fuel additive. See this thread.
PGP Key and corresponding e-mail address
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Formatik
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Propylene: 200g isopropanol are let sit for 24 hours with 650 g melted ZnCl2, and then are heated (Friedel, Silva, Jahresberichte, 1873, 322). Drip
eventually 4 pts propyl alcohol onto 3 pts P2O5 (Beilstein, Wiegand, Ber. 15, 1498). From allyl bromide or 1-bromopropylethyl ether by addition of Zn
dust in 95% pure ethanol (Ber. 31, 3071), etc. According to an older reference I’ve found, propylene also forms by heating isopropanol with an
excess of conc. H2SO4, just like by ethylene with ethanol (Graham-otto's ausführliches Lehrbuch der Chemie by Julius Otto, Thomas Graham, pg. 324).
For propylene oxide, there is also a way of obtaining it directly from propylene and H2O2 and catalysts, e.g. USP5599955.
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497
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I like that idea Polverone, it just requires bubbling HCl through hot propylene glycol? Do you know anything more about it like yield, time, temp,
etc?
My current plan goes something like this:
Figure out source of propylene (main problem)
Extract HOCl from solution with MEK or acetone
React HOCl with propylene in the ketone (does it need water?) to form the chlorohydrin
Distill off ketone
React with a base to form propylene oxide.
If Polverone's method is practical, it will simplify things greatly. If it doesn't work out then I'll have to try the old sulfuric acid dehydration...
And if that doesn't work I'll have to try a gas phase dehydration over a catalyst. What about other more powerful water absorbers like B2O3 or HPO3?
Maybe they'd work better?
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kclo4
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| Quote: |
Extract HOCl from solution with MEK or acetone
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Whaaa???
http://en.wikipedia.org/wiki/HOCl
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Polverone
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| Quote: | Originally posted by 497
I like that idea Polverone, it just requires bubbling HCl through hot propylene glycol? Do you know anything more about it like yield, time, temp,
etc?
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I'd suggest spending a couple of hours on Google Books, keeping in mind that there's not really a consistent nomenclature for the materials you're
interested in. IIRC I found numerous references, some quite detailed, to forming ethylene chlorohydrin from the boiling glycol using HCl gas. There
were a number that indicated propylene glycol would work similarly.
I read quite a bit on Google Books about these reactions some months ago but I don't recall the specifics. There should be plenty of information in
books found on Google Books and archive.org though.
PGP Key and corresponding e-mail address
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ScienceSquirrel
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Reaction of propylene-1,2-glycol with a suitable reagent should result in the formation of 2-chloropropan-1-ol in high yield.
Reaction with a suitable base should form propylene oxide.
After that reaction with benzene and a catalyst to yield 1-phenylpropan-2-ol should be a breeze 
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497
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Thanks Polverone, I will do that.
A good patent on continuous vapor phase alchohol dehydration is US Patent 2377026. The catalyst looks quite easy to make too.
Look up US Patent 3578400. It looks pretty useful for any reaction that needs
pure HOCl. I was surprised at first too.
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kilowatt
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You can buy cylinders of propylene from welding suppliers. Around here it is sold as "HPG" gas. It's about $90 for 27lbs.
The mind cannot decide the truth; it can only find the truth.
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turd
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| Quote: | Originally posted by ScienceSquirrel
After that reaction with benzene and a catalyst to yield 1-phenylpropan-2-ol should be a breeze |
Regioselectivity?
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S.C. Wack
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Looks pretty high. Maybe someone has Springer access.
http://dx.doi.org/10.1134/S1070427206030141
Bromobenzene Grignard reagent likewise gives 1-phenyl-2-propanol as the only alcohol, and in the same chiral purity as the epoxide.
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sparkgap
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Here be the paper...
...that Mr. Wack was referring to.
sparky (~_~)
Attachment: syntharalk.pdf (56kB)
This file has been downloaded 1654 times
"What's UTFSE? I keep hearing about it, but I can't be arsed to search for the answer..."
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Nicodem
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Regarding propylene glycol to propylene chlorohydrin, I will cite myself:
| Quote: | Originally posted by Nicodem
It seams it might be possible to make 1-chloropropan-2-ol by bubbling HCl trough 1,2-propanediol at about 110°C. At least by analogy with glycerol as described at Org. Synth. Glycerol can actually even be dichlorinated up to 1,3-dichloropropan-2-ol. There is no reason why this would not work with 1,2-propandiol as well under the same conditions.
1-chloropropan-2-ol is an interesting compound that can be used to prepare a useful reagent, propene oxide. |
From http://sciencemadness.org/talk/viewthread.php?tid=6455
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unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
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497
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Thank you, I looked for the procedure on google books and was unable to find any that were viewable.
Do you know if a small amount of water being present from not completely dry HCl or glycol would be a problem? And I don't have glacial acetic acid..
Maybe it would proceed without it?
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497
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I wonder if it would be possible to produce the HCl in situ with NaHSO4 and NaCl(or any other suitable chloride)? They are probably slightly soluble,
maybe enough to react, or a little water could be added. I don't believe either salt or the resulting Na2SO4 would react with the glycol or
chlorohydrin, but I could be wrong. It would seem the produced HCl would have a very large amount of contact with the glycol, if all goes as I think
it would.
I would really like to avoid the separate HCl generator if I can. If I am forced to use it, would NaHSO4/NaCl be able to produce dry enough HCl? Maybe
dry it with a little CaCl2? Since I would need a pretty large quantity of HCl, I'd like to avoid having to use multiple gallons of concentrated H2SO4
and Hydrochloric acid any way I can...
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vulture
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Bubble your HCl gas through H2SO4 and it should be dry enough.
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not_important
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The Org. Synth. reference Nicodem includes | Quote: |
An alternative procedure which is slower and gives slightly lower yields, but which does not require a hydrogen chloride generator...
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using concentrated hydrochloric acid and acetic acid. The organic acid appears to be needed.
It should be noted, given that most preparations involve reflux, that the simple chlorohydrins are somewhat toxic; good ventilation and gloves would
be wise.
http://www.cdc.gov/niosh/idlh/107073.html
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octave
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Could it be possible to depolymerize polypropylene(http://www.freepatentsonline.com/4624993.html) and then follow the first method suggested in (bad source I know) http://en.wikipedia.org/wiki/Propylene_oxide ? If it would work,which I doubt, then it would be rather easy and cheap as all chemicals required
are very readily available.
[Edited on 17-8-2008 by octave]
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not_important
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The poly-olefins tend to give larger hydrocarbons than the original olefins; you get a gasoline or diesel like mixture with little C3 hydrocarbon.
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497
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I read a paper about the decomposition products of PP a while ago. It resulted a soup of maybe 30 different hydrocarbons, none of which made up a very
large fraction of the whole (some 0.1% others 10%). I don't think propylene was even on the list.
I like the alternative procedure except that it requires refluxing a very corrosive mixture. Since I don't have a glass condenser, this might be hard
to rig up. I suppose I'll figure something out.
Since I really don't like the idea of a vacuum fractional distillation of the resulting product I'm thinking I'll just distill at standard pressure
until most of the HCl is gone and then add Ca(OH)2 to make propylene oxide which will hopefully be easy to distill out. Will this work even with the
glycol still present?
The whole thing will definately be done outside.
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MagicJigPipe
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I'm sorry if this has been mentioned as I don't have time to read the entire thread at this point in time...
Propylene (most likely impure, but hey, when has that stopped us before?) can be purchased at just about any welding supply shop by the cylinder.
It's more expensive now (for obvious reasons) but still, it's not too bad. Apparently even some hardware stores sell small cylinders of propene.
What I would do is buy it and focus more of my efforts on cleaning it up. Imagine how much easier it would be to have propene "on tap" as opposed to
relying on a reaction.
EDIT
Also, propylene oxide can be purchased online. It is EXTREMELY rare and there's only one place that I know of that still has it. U2U me if you want
the source as I don't want to possibly make it go bye bye by posting it publicly.
[Edited on 8-17-2008 by MagicJigPipe]
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
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free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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Formatik
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HCl from bisulfates
Molten KHSO4 (Mp. 210ºC) reacts with KCl under formation of HCl (E. Mitscherlich, Pogg. Ann. 18 [1830] 152). Tried it with NaHSO4 and NaCl (together
melted gave fog with NH3, where NaHSO4 melted alone did not), both bisulfates are also hygroscopic so could have some water content already.
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