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Author: Subject: Preparation of elemental phosphorus
clearly_not_atara
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[*] posted on 17-4-2021 at 07:04


I don't know what you mean by "small scale". It's hard enough to deal with electricity at high temperatures, and even a kilo of MgCl2 isn't breaking anybody's budget. You need all kinds of insulation and temperature control, so it's simpler to set up the equipment to hold around a liter of molten salts anyway. At that scale, you get a few grams of P per run, which really isn't bad.

The big advantage of not running a "bomb" process like carbo/metallothermal reduction is that the damage to equipment and clean-up should be much less.




[Edited on 04-20-1969 by clearly_not_atara]
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Triflic Acid
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[*] posted on 27-4-2021 at 05:55


You know, maybe setting the system up so that you occasionally top it off a mixture of chloride and phosphate would allow you to keep going indefinitely. Also, I found two papers that give a pretty good idea: https://www.sciencedirect.com/science/article/pii/S092702481... for the euctic, and https://pubs.rsc.org/en/content/articlelanding/2009/gc/b9063... for the electrostablility of the euctic. The first paper basically says that a choline chloride euctic works. The second paper I found a bootleg copy of online. Any thoughts? Looks promising to me.

Attachment: Greenchemistrypublished.pdf (210kB)
This file has been downloaded 288 times





There wasn't a fire, we just had an uncontrolled rapid oxidation event at the power plant.
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njl
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[*] posted on 27-4-2021 at 06:18


Atara, if you do the math: 2 percent solution of Ca3(PO4)2 in 1 Kg molten salt = 20 grams Ca3(PO4)2 = .0645 mols. With 100 percent recovery of phosphorus that's 1.9 grams per run. What I mean by small scale is 1 Kg. Or 10 Kg for that matter. Not to mention even if one gets this to work you have to deal with gaseous WP.



Reflux condenser?? I barely know her!
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clearly_not_atara
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[*] posted on 27-4-2021 at 09:04


njl: You've used a density of 1 for the molten salt (I said "liter", you said "kilogram"), which is only a little wrong when you're dealing with organic chemicals, but the density of alkali chloride salts is about 2-2.5, which raises your raw numbers to about 4 grams. There was also a proposal of using (NaPO3)x as the phosphorus source instead of CaPO4, which may significantly increase the phosphorus content (unclear).

For amateur-feasibility, we are already forced to improvise because 850 C is a difficult temperature. It is also plausible that the reaction doesn't work at all at lower temperatures. But while we're on the subject, the KCl-LiCl eutectic is shockingly low: 352 C!
https://pubs.acs.org/doi/pdf/10.1021/ja01538a001

In this context, it's worth remembering that elemental phosphorus is a precursor to various reagents and catalysts that support difficult reactions under mild conditions in high yield on delicate substrates. A few grams of phosphorus is all you need to make a lot of PPh3-ligated catalysts, for example.

The gaseous WP thing is a moot point because all practical phosphorus refinement techniques give a gaseous product. Electrolysis should give WP at a lower temperature and in higher purity than carbothermal reduction.

Triflic Acid: Neither of these papers shows anything about choline chloride being effective at the potentials required for phosphate reduction...




[Edited on 04-20-1969 by clearly_not_atara]
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[*] posted on 27-4-2021 at 09:06


Is no one thinking about the euctic :mad: Why would it be gaseous WP if it is a euctic. WP boils at 280C, and with a bit of work a euctic could be made so that it is liquid below this temp. Also, constantly topping up the CaCl2 with Ca3(PO4)2 would let you get out more than 1.9g per kg. Even then, this could be played around with to get a better ratio of chloride to phosphate, by trying different cations like sodium. I think that this is worth trying. I'll post when I get around to trying this.



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clearly_not_atara
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[*] posted on 27-4-2021 at 10:14


See ref for LiCl-KCl eutectic production reference:

https://iopscience.iop.org/article/10.1149/1.2428639/meta?ca...

352 C is pretty good; it's not at all difficult to condense something coming over at 400ish. I think that getting the working temperature safely under 500 C opens up a lot of doors, because a lot of equipment is rated to around 500 C.

The truth is that if the phosphorus product weren't gaseous you'd have a whole host of new problems, like whether it passivates the cathode, reacts with the membrane, forms complex dissolved salts, floats, sinks, foams, etc.




[Edited on 04-20-1969 by clearly_not_atara]
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[*] posted on 27-4-2021 at 10:29


I don't know, I'm thinking that, assuming that the P floats, we could just have an inverted test tube over the cathode, like in a hofmann voltmeter. Airtight and to remove the white P you just flood with water and remove the test tube. On the other hand, if it sinks, just flip the test tube over and the white P will collect under the euctic, still airtight and easy to collect.

[Edited on 27-4-2021 by Triflic Acid]




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[*] posted on 27-4-2021 at 10:37


Yes, I think it would be necessary to remove the phosphorus as it forms by distilling it off. But this means that the cell and distillation apparatus must be well sealed against the atmosphere and evacuated. That's the problem with this batch process, there's no convenient way to periodically add phosphate without disassembling the entire setup. Unlike in a retort where the atmosphere within the apparatus is consumed (leaving an inert space for distillation) this design reintroduces oxygen with every batch (which again have a yield of maximum 1.9 grams WP). There is a lot of room for improvement, but I can't see how this would be practical until at least the yield per batch is optimized.



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[*] posted on 20-2-2022 at 13:12


I took 60um silicagel for chromatographic purpose calcined it at 1200°C for 15min
60um (unreactive) aluminum powder
Na3PO4*12H2O mixed with H3PO4 based rust remover to get NaH2PO4, this heated to 200°C for 4 hours then 800°C for 30mins, there were small flaming pops at 800°C indicating that there were organic crap in the rust remover.

This was mixed in 3,4 NaPO3 1,75 Al 1 SiO2 weight ratio, ball milled for 4 days in acetone, then dryed

10g of said powder packed into alufoil the pack is fixed into a qartz tube, top end was purged countinously with CO2 bottom was immersed to about 10cm water

I started the raction by heating the quartz tube at one spot, when the reaction started, some expansion of the slag took place clogging up the quartz tube, then shooting out the top plug, then at the bottom the gases escaping the water bottle instantly catched fire, after cooling there were only a sub gram quantity of P4 at the bottom of the collector. I removed the slag from the tube and it instantly catched fire maybe a gram worth of white P4 was still inside the tube estimating by the amount of smoke:) After the whole mess I scanned the desktop with a bunsen burner and there were small pops and sparks all around the table. A lot of things on the table catched fire/made a small flash during the cleanup here and there, so I only recommend repeating this if you have a shitty garage like me and you do not mind making it inhabitable for a while:)
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[*] posted on 20-2-2022 at 22:33


Quote: Originally posted by clearly_not_atara  

In this context, it's worth remembering that elemental phosphorus is a precursor to various reagents and catalysts that support difficult reactions under mild conditions in high yield on delicate substrates. A few grams of phosphorus is all you need to make a lot of PPh3-ligated catalysts, for example.


If PPh₃ is what you need, there’s no need to fancy weird or risky reactions. It can be bought easily here, and it is quite cheap.
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[*] posted on 8-5-2022 at 10:35


I modified above procedure as follows:
Ignited silical gel was replaced with expired transparent saniter silicone (caulk in US terms I think) that was burned to SiO2 on a pan.
Na3PO4 was treated with pure H3PO4 then dryed and ignited in a SS bowl to give presumably NaPO3 of something similar, it is a transparent glass that breaks on cooling to 2-3cm bits.

The Al SiO2 NaPO3 mixture was poured into the ball mill with some hexane instead of acetone, acetone reacts with Al during the milling process evidenced by evolution of H2.

The mixture was milled for 6 days, hexane was recovered @ 90°C, the powder then dryed @ 45°C for 4 hours, the initially inert grey powder turned black it is as easily ignited as black powder, also impact sensitive, a moderate blow from a hammer can set it off.

Igniting this gave off white smoke and beneath the pile there was a stain of phosphorous by scraping the stain it gave off small flashes. It is good to make some smoky stuff with this for new years eve but i think it is too aggressive to isolate P from this, maybe diluting the mixture with some carbon can curb the burn rate, pressing it into pellets can also help.
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clearly_not_atara
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[*] posted on 27-6-2022 at 19:56


https://chemistry-europe.onlinelibrary.wiley.com/doi/pdfdire...
"The Dean–Stark esterification of H3PO3 with 1-butanol (1.5 equiv.) gave a mixture of H3PO3, HOP(O)(OBu)H, and (BuO)2P(O)H in a 11:56:33 molar ratio."

Okay, it's not quite phosphorus, but sodium phosphite is OTC in some places. The dialkyl H-phosphonates can most likely be brominated or chlorinated to the dialkyl halophosphates, offering the possibility to activate a wide variety of carboxylic acids, alcohols, phenols, oximes, etc, as would be done with POCl3. Trialkyl phosphates, hiterto considered impossible, would also be accessible.

In the particular case of trimethyl phosphate, I don't know if the esterification of methanol with phosphorous acid works, or if the boiling point is too low.




[Edited on 04-20-1969 by clearly_not_atara]
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