CEY-19
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Phosphorus halides from phosphine
Hey guys,
Long time lurker, first time poster. Recently I've been interested in finding a way to prepare PCl3 and PBr3 without having to
face the hassle of either preparing elemental phosphorus or of collecting it from matchboxes.
Whilst looking into a few possibilities, I found a patent (US6685904: Process for making phosphorus halides and oxyhalides) which outlines a process of reacting PH3 with Cl2 in the
presence of H2 at various temperatures in a quartz tube to produce PCl3 and HCl, the extra hydrogen being present as a diluent
possibly, but mostly as a relic of the process of phosphine production the authors of the patent used. In theory, one could use undiluted phosphine if
one planned, as I do, to get their phosphine some other way.
I was wondering if anyone had attempted this reaction themselves?
I was planning on using the 1:1:3 mixture of PH3:H2:Cl2, supplying the hydrogen and phosphine separately and mixing
them before drying them, and using an old Graham condenser I have lying around as a reaction vessel with hot water running through the "cooling"
jacket, with a separatory funnel serving as a collection flask to allow easy transfer to ampoules. Excess unreacted gas would be drawn off and burned
through an old bunsen isolated from the gas generators and reaction chamber.
Does anything about that strike anyone as dangerous or ill advised? The system will be flushed out with excess hydrogen to remove any unreacted
lingering phosphine and drive it out to the bunsen once the reaction is complete.
Would love to hear your thoughts and get a few sets of fresh eyes on the whole thing, personally.
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byko3y
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You can make PCl3 by chlorination of phosphide.
"Small-Scale Synthesis of Laboratory Reagents with Reaction Modeling", Leonid Lerner. Chapter 18. Phosphorus Pentachloride.
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CEY-19
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Useful to know, and logged for consideration, though I was planning to get my phosphine from sodium phosphinate as I have some of that around from
some experiments many moons ago. My only source of phosphide would be either importing mole killer (expensive and only a few percent phosphide) or
trying to prepare some myself (unnecessary hassle).
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Magpie
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You are planning to generate three gas streams simultaneously, regulating flow of each to obtain the said ratio? When the Cl2 oxidizer comes in
contact with the reductants you will produce a controlled (hopefully) combustion process.
This sounds complex and demanding. Do you have experience in such endeavors?
The single most important condition for a successful synthesis is good mixing - Nicodem
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CEY-19
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Quote: Originally posted by Magpie  | You are planning to generate three gas streams simultaneously, regulating flow of each to obtain the said ratio? When the Cl2 oxidizer comes in
contact with the reductants you will produce a controlled (hopefully) combustion process.
This sounds complex and demanding. Do you have experience in such endeavors? |
The important ratio to maintain is the ration of phosphine to chlorine, the hydrogen concentration is not as vital. I plan on running the reactor
chlorine lean so as to prevent the formation of the pentachloride.
The reaction isn't so much a controlled combustion (which would presumably take place at much higher temperatures) but a more controlled
chlorination, taking place at temperatures below 100°C.
Ultimately I plan to control the mixture by controlling the rate of chlorine generation and letting the phosphine/hydrogen mixture flow remain fairly
constant.
That said, it is fairly complex and I must admit I have never done anything quite similar. I've used bromine and methane to prepare some bromomethane
using a roughly similar method with UV irradiation to a quartz tube, that's about as close as I got, and it wasn't massively successful. More for
interest than for proper use.
[Edited on 2015-7-20 by CEY-19]
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Magpie
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Hot phosphine self-ignites in atmospheric air producing a loud "pop."- I know this by experience when making phosphorus in a furnace. Have you
computed the heat of reaction of phosphine with Cl2?
Do you plan on running this continuous process at a sufficiently slow rate that heat removal will not be a concern? You say that you will be using
hot water in the condenser jacket - so I guess you are not worrying about too much heat. The coil of a Graham is a rather restricted space. I guess
you are not concerned with surges that would cause small explosions?
The single most important condition for a successful synthesis is good mixing - Nicodem
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CEY-19
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Yes, the gas phase heat of reaction is 565.6kJ mol-1, less than half the heat of combustion of phosphine in oxygen (closer to 1200kJ
mol-1). The reaction rate is being kept slow, yes, so heat production is not a massive concern. The reaction is apparently not explosive so
long as some hydrogen dilutant gas is present.
"The chemists are a strange class of mortals, impelled by an almost insane impulse to seek their pleasures amid smoke and vapor, soot and flame,
poisons and poverty; yet among all these evils I seem to live so sweetly that may I die if I were to change places with the Persian king." - Johann
Joachim Becher
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unionised
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Hydrogen and chlorine will explode if mixed and ignited. Phosphine and chlorine will almost certainly do so too.
Why would diluting one (probably) explosive mixture with another (known) explosive mixture stop it going bang?
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CEY-19
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They aren't being ignited: the reaction is more akin to a chlorination than to burning one in the other to my understanding. The reaction takes place
at a low enough temperature that chlorine does not even react with the hydrogen present. This, of course, is if the patent is to be believed, which
for the initial runs I do not plan to trust. Slow addition of the chlorine to the hydrogen/phosphine will precede any proper runs, in order to test
the possibility of explosions. Blast shield at the ready.
As a note, I do not know whether or not the phosphine/chlorine mixture will be explosive: I know that in 2008 woelen posted a page on his site of a
reaction between chlorine and phosphine under wet conditions which did give spontaneous combustion. It is thus my speculation that if the patent can
be believed, the hydrogen is playing some role in preventing this combustion. However, it could also be the exclusion of moisture which prevents the
spontaneous combustion, or it may be that the patent is instead patent nonsense...
"The chemists are a strange class of mortals, impelled by an almost insane impulse to seek their pleasures amid smoke and vapor, soot and flame,
poisons and poverty; yet among all these evils I seem to live so sweetly that may I die if I were to change places with the Persian king." - Johann
Joachim Becher
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Ozone
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It will probably blow up.
Anyhow, you want to avoid blue vis or UV light--the H2 + Cl2-->2HCl rxn is easily initiated photochemically (an old, particularly striking
laboratory demo). The reaction is violent.
So, if you must do this, do it in the dark or under filtered red-light.
See: https://www.youtube.com/watch?v=NN82GoBG98s
Cheers,
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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CEY-19
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| Quote: Originally posted by Ozone | It will probably blow up.
Anyhow, you want to avoid blue vis or UV light--the H2 + Cl2-->2HCl rxn is easily initiated photochemically.
|
Yeah, seems like the chance of an explosion is pretty high on this, planning on doing it outside, night time. Originally, so I could see any signs of
more combustion-type behavior, but the additional thought of the possibility of blue light setting off the Cl2/h2 is a good one
so you have my thanks.
Blast shields at the ready and cheap glassware means if it does go off I mostly just have to play thousand piece pick up haha
"The chemists are a strange class of mortals, impelled by an almost insane impulse to seek their pleasures amid smoke and vapor, soot and flame,
poisons and poverty; yet among all these evils I seem to live so sweetly that may I die if I were to change places with the Persian king." - Johann
Joachim Becher
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AJKOER
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| Quote: Originally posted by CEY-19 | | Quote: Originally posted by Ozone | It will probably blow up.
Anyhow, you want to avoid blue vis or UV light--the H2 + Cl2-->2HCl rxn is easily initiated photochemically.
|
Yeah, seems like the chance of an explosion is pretty high on this, planning on doing it outside, night time. Originally, so I could see any signs of
more combustion-type behavior, but the additional thought of the possibility of blue light setting off the Cl2/h2 is a good one
so you have my thanks.
Blast shields at the ready and cheap glassware means if it does go off I mostly just have to play thousand piece pick up haha |
My research on H2/Cl2/sunlight (especially red light) is that light can indeed initiate an explosive chain reaction. However, a lecture I once read on
chain reactions (may still be available somewhere on the web) did also indicate a small amount of O2 interjects a termination step into the otherwise
explosive chain reaction sequence.
But unfortunately, oxygen may not be a life saver here because if its interaction with PH3 (Edit: more accurately, the presence of P2H4 impurity may
be responsible for spontaneous ignition, see http://phosphorus.atomistry.com/hydrogen_phosphides.html in air, which apparently can also occur with PH3 at reduced pressures). However, PH3
itself may act in the role of a spoiler in place of O2, so no explosion may actually take place. Best to test out on a very small scale a few times to
be sure.
--------------------------
A comment from Atomistry.com on PCl3 on its preparation (link: http://phosphorus.atomistry.com/phosphorus_trichloride.html ):
"It is possible to prepare it directly from calcium phosphate by heating this with silica and charcoal and passing over it the vapour of sulphur
monochloride:—
4S2Cl2 + Ca(PO3)2 = 2PCl3 + CaCl2 + 3SO2 + 5S "
Note, Atomistry on S2Cl2 (link: http://sulphur.atomistry.com/sulphur_monochloride.html ) to quote:
"Sulphur and chlorine interact slowly at the ordinary temperature but much more readily on warming. The customary procedure is to pass dried chlorine
into fused sulphur or over dry " flowers of sulphur " until most of the sulphur has disappeared. The resulting monochloride contains considerable
amounts of higher sulphur chlorides in solution, but if the mixture is heated for some time under a reflux condenser the pure monochloride can
subsequently be distilled over. "
----------------------------
Also, an interesting path to P suggested also via PCl3 in the same Atomistry link, to quote:
"....antimony, phosphine and arsine, giving phosphorus in each case."
which implies to me the reaction:
PCl3 + PH3 = 2 P + 3 HCl
But the same link also states:
"Heating phosphorus in a sealed tube with HCl:—
2P + 3HCl = PCl3 + PH3 "
so to favor the reaction direction in formation of Phosphorous, cooling may work along with an absence of any water as to quote the same source:
"PCl3 + 3H2O = H3PO3 + 3HCl "
[Edited on 21-7-2015 by AJKOER]
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AJKOER
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| Quote: Originally posted by CEY-19 | | Quote: Originally posted by Ozone | It will probably blow up.
Anyhow, you want to avoid blue vis or UV light--the H2 + Cl2-->2HCl rxn is easily initiated photochemically.
|
Yeah, seems like the chance of an explosion is pretty high on this, planning on doing it outside, night time. Originally, so I could see any signs of
more combustion-type behavior, but the additional thought of the possibility of blue light setting off the Cl2/h2 is a good one
so you have my thanks.
Blast shields at the ready and cheap glassware means if it does go off I mostly just have to play thousand piece pick up haha |
My research on H2/Cl2/sunlight (especially red light) is that light can indeed initiate an explosive chain reaction. However, a lecture I once read on
chain reactions (may still be available somewhere on the web) did also indicate a small amount of O2 interjects a termination step into the otherwise
explosive chain reaction sequence.
But unfortunately, oxygen may not be a life saver here because if its interaction with PH3. Edit: More accurately, the presence of P2H4 impurity
(which can reportedly be removed by washing the gas mixture with concentrated HCl) may be responsible for spontaneous ignition (please see Atomistry
on P2H4 at http://phosphorus.atomistry.com/hydrogen_phosphides.html ) in air, which apparently can also occur with PH3 at reduced pressures. However, PH3
itself may act (speculation) in the role of a spoiler in place of O2, so no explosion may actually take place. Best to test out on a very small scale
a few times (after scrubbing the gas mixture with HCl) to be sure.
----------------------------
A comment from Atomistry.com on PCl3 on its preparation (link: http://phosphorus.atomistry.com/phosphorus_trichloride.html ):
"It is possible to prepare it directly from calcium phosphate by heating this with silica and charcoal and passing over it the vapour of sulphur
monochloride:—
4S2Cl2 + Ca(PO3)2 = 2PCl3 + CaCl2 + 3SO2 + 5S "
Note, Atomistry on S2Cl2 (link: http://sulphur.atomistry.com/sulphur_monochloride.html ) to quote:
"Sulphur and chlorine interact slowly at the ordinary temperature but much more readily on warming. The customary procedure is to pass dried chlorine
into fused sulphur or over dry " flowers of sulphur " until most of the sulphur has disappeared. The resulting monochloride contains considerable
amounts of higher sulphur chlorides in solution, but if the mixture is heated for some time under a reflux condenser the pure monochloride can
subsequently be distilled over. "
Also, to quote:
"Phosphorus trichloride reacts with sulphur monochloride, iodine acting as a catalyst; the products are phosphorus pentachloride and phosphorus
sulphochloride:
3PCl3 + S2Cl2 = PCl5 + 2PSCl3 "
So, absence an Iodine catalyst, excess S2Cl2 should not significantly reduce the yield of PCl3.
----------------------------
Also, an interesting path to P suggested also via PCl3 in the same Atomistry link, to quote:
"....antimony, phosphine and arsine, giving phosphorus in each case."
which implies to me the reaction:
PCl3 + PH3 = 2 P + 3 HCl
But the same link also states:
"Heating phosphorus in a sealed tube with HCl:—
2P + 3HCl = PCl3 + PH3 "
so to favor the reaction direction in formation of Phosphorous, cooling may work along with an absence of any water as to quote the same source:
"PCl3 + 3H2O = H3PO3 + 3HCl "
[Edited on 21-7-2015 by AJKOER]
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CEY-19
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| Quote: Originally posted by halogen |
chlorinate a metallic phosphide solid like byko suggested, from which one assumes you'd prepare the phosphine anyways.
[Edited on 21-7-2015 by halogen] |
As previously noted, I'd be using sodium phosphinate and not a phosphide as that is what I have access to.
"The chemists are a strange class of mortals, impelled by an almost insane impulse to seek their pleasures amid smoke and vapor, soot and flame,
poisons and poverty; yet among all these evils I seem to live so sweetly that may I die if I were to change places with the Persian king." - Johann
Joachim Becher
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woelen
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How can sodium phosphinate (sodium hypophosphite) be used to make a steady flow of PH3? That would be interesting on its own. Sodium hypophosphite is
cheap for me and I can buy it at kg-quantities without problems. I never considered it really interesting because of its rather sluggish reactions in
aqueous solutions.
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byko3y
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H2(PHO3) + Zn (H2SO4) => PH3 + 3H2O
The reaction is pretty much a reversal of PH3 + 2 I2 + 2 H2O => H3PO2 + 4 HI.
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AJKOER
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Per Wikipedia on NaH2PO2 (link: https://en.m.wikipedia.org/wiki/Sodium_hypophosphite ):
"Sodium hypophosphite should be kept in a cool, dry place, isolated from oxidizing materials. It decomposes when heated and produces toxic phosphine
gas, causing irritation to the respiratory tract.
2 NaH2PO2 → Na2HPO4 + PH3"
So phosphine gas is but an irritant?!??
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byko3y
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AJKOER, phosphine has a definite disagreeable odor, but in case you continue to breath it in for a long period of time - you will be poisoned and
maybe even die.
In fact, the odor is tolerable and some people are ignorant enough to ignore it. Natural selection in action.
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